Is there mismatch in injures or death numbers for carnivores that hunt during day time and night time?

Is there mismatch in injures or death numbers for carnivores that hunt during day time and night time?

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Is there significant mismatch in injures or death numbers for hunters (when hunter was killed or injured by its prey), between day time and night time hunts (carnivores that hunt during the day time and night time)?

Gray Wolf

Yellowstone National Park ensures the long-term viability of wolves in Greater Yellowstone and provides a place for research on how wolves may affect many aspects of the ecosystem.

Although wolf packs once roamed from the Arctic tundra to Mexico, loss of habitat and extermination programs led to their demise throughout most of the United States by the early 1900s. In 1973, the U.S. Fish and Wildlife Service (FWS) listed the northern Rocky Mountain wolf (Canis lupus) as an endangered species and designated Greater Yellowstone Ecosystem (GYE) as one of three recovery areas. From 1995 to 1997, 41 wild wolves from Canada and northwest Montana were released in Yellowstone. As expected, wolves from the growing population dispersed to establish territories outside the park, where they are less protected from human-caused mortalities. The park helps ensure the species’ long-term viability in GYE and has provided a place for research on how wolves may affect many aspects of the ecosystem. January 12, 2020, marked the 25th anniversary since wolves returned to Yellowstone.

Wolves (back) are larger than coyotes (middle) and red foxes (front).

Yes, Lions Will Hunt Humans if Given the Chance

Earlier this week, a female African lion attacked and killed a 29-year-old American woman on safari outside Johannesburg, South Africa. It's a tragedy, but given what zoologists know about lions, not one that's totally unexpected.

Related Content

While visiting a lion reserve on a car tour, the woman rolled her window down to take some pictures, according to Brent Swails and Dana Ford of CNN. She likely did not see the lioness approach. The animal stopped three feet from the vehicle before lunging through the window. A guide, who was also in the car, tried to fight the animal off, sustaining injuries to his arm. Staff chased the lioness away, and the woman died at the scene. Signs in the park warn visitor to keep their windows rolled up, and the part has had previous incidents stemming from open windows.

While the facts of the attack are horrible, the lioness didn't do anything that's inconsistent with her biology, as Mary Bates explains for National Geographic. Lions are extremely accomplished predators and adept hunters. For them, humans count as prey. Ignoring their prowess in this department is a big mistake. Luke Dollar, a conservation scientist who directs the National Geographic Society's Big Cats Initiative, told Bates. "Almost any organism around lions might be a potential prey item, and for people to think that they are an exception is folly" Dollar said.  "I would imagine that every other primate that co-exists with big cats is acutely aware of the position they hold relative to the top predators of the world."

Given the intersection of tourism and conservation at sites like the lion park, humans sometimes acquire a false sense of security. As society expands to less developed areas, humans, lions and other predators have also inevitably crossed paths more frequently.

Since not all attacks are reported, it's hard to put numbers on the number of lion attacks seen globally. Estimates range from 20 to 250. Tanzania has the highest population of lions in Africa, and between 1990 and 2004, the country saw 593 deaths and 308 injuries from African lion attacks.

Aside from lack of awareness on the part of the human, there are a few things that might drive a lion to attack a human. The first and most obvious is hunger. Without horns or fangs, humans also look like easier targets to older or sick lions. In certain instances, females might perceive humans as a threat to their cubs. If the animal is injured, it also might feel threatened by the presence of a human.

Though an investigation of the attack continues, park officials told SABC News that they do not plan to execute the lioness involved in this week's attack. Instead, she will be moved to a private part of the park.

Dollar told Bates he hopes that the attack can at least raise awareness among tourists and encourage people to be careful while out observing the impressive predators in the wild.

About Helen Thompson

Helen Thompson writes about science and culture for Smithsonian. She's previously written for NPR, National Geographic News, Nature and others.


Large carnivores facilitate biodiversity [1–3], but they can threaten human safety by injuring or killing people. This is the most dramatic form of wildlife-human conflict, a source of public opposition to large carnivore conservation, and a challenge for carnivore management [4–7]. Human persecution and habitat loss have endangered large carnivore populations worldwide [8,9], but some are recovering, exacerbating old conflicts [10,11]. Historically, attacks on humans have been a major source of human conflict with large carnivores [12] and increasing rates of attacks by some species [7,13] undermine large-carnivore protection efforts and population recovery on several continents. The issue is therefore of broad concern for conservation and management, in addition to human safety.

Although more people are killed by species such as domestic dogs, horses, cattle, or snakes than by bears [14,15], the attitudes of people towards bears and other large carnivores reflect their concerns about personal safety. Rareness of attacks also contribute to generate much media attention, which can influence people’s attitudes [16,17]. How people perceive the risk of attack affects the tolerance they have for conservation efforts [18–20] and, although efforts have been made to try to reduce human fear of large carnivores [21], it is essential to provide managers and the public with accurate information regarding the risks that carnivores pose to people in order to reduce these risks.

Here we present the case of the Scandinavian brown bear (Ursus arctos) population, which increased to

3300 bears by 2008 in Sweden [22], where > 95% of Scandinavian bears live, after near extirpation around 1930 [23]. Nowadays there are

2800 bears in Sweden [24]. Injuries from bear attacks have increased during the last decades and fatalities have been documented for the first time for more than 100 years [15,25]. Repeat questionnaires reveal that public fear of large carnivores is increasing [26,27].

Brown bears are hunted in Scandinavia [28] and hunters have been the most affected by bear attacks, compared to other outdoor users [15]. After a fatal incident in 2004, hunters in Sweden focused on dangers associated with hunting bears and hunting in areas with bears, resulting in information campaigns and, since 2007, annual hunting courses focusing on bear behavior and safety when encountering bears. In this paper we review all incidents where bears have caused human injuries or fatalities in Scandinavia from 1977 to 2016 and evaluate how brown bear population trends, number of hunters and nonhunter outdoor users, education of hunters, and other risk factors based on bear ecology may have influenced the number of injuries and fatalities in the last four decades. Our goal is to provide information that can help avoid new incidents, which is both of management and conservation interest.

Origin, History, and Culture

The work of geneticists, archeologists, and historians have contributed to our understanding of the origin and timing of lions' colonization of the Indian subcontinent. Evidence from the three disciplines do not always corroborate each other and there is still a lot to learn about when and how lions came into India. Two subspecies of extant lions, namely all lions from Africa as P. l. leo and lions from Asia as P. l. persica were recognized (Bauer et al., 2016). These were believed to have diverged sometime between 55,000 and 200,000 BP (Oɻrien et al., 1987). Recent investigations on phylogeography of modern lions, based on mitochondrial and nuclear DNA analysis, indicates a single African origin of modern lions (Barnett et al., 2006 Antunes et al., 2008). Extant lions originated from several Pleistocene refugia (324,000�,000 BP) in East and South Africa (Antunes et al., 2008). Asiatic lions are believed to have originated from an older East African refuge dispersal event some 118,000 BP (95% CI 28,000�,000 BP) (Antunes et al., 2008). Based on Northern, Western and Central African lions' close genetic proximity to extant Indian lions as compared to Southern and East African lions, Bertola et al. (2011) postulated an alternative explanation, wherein after a Pleistocene extinction event in Western and Central Africa, recolonization occurred from a refugia in the Middle East. More recent analysis of mt-DNA from modern and ancient lion samples (Barnett et al., 2014) shows that lion exodus into Asia started as late as 21,000 BP and probably continued till the late Holocene. Maternal lineage of Gir lions was found to be nested within the clade formed by Northern, Western, and Central African lions (Barnett et al., 2014). Bertola et al. (2015) included nuclear markers along with mt-DNA and found lions from India to form a distinct cluster with little/no admixture with African lions. The IUCN Cat Specialist Group now recognizes two subspecies P. leo leo consisting of lions from India, Central and West Africa and P. leo melanochaita comprised of lions from Eastern and Southern Africa (Kitchener et al., 2017). Fossil records in Sri Lanka (Manamendra-Arachchi et al., 2005) report lion and tiger presence as early as the late quaternary, much before the current estimated arrival of both modern lions and tigers into India. The last land bridge between India and Sri Lanka submerged 5,000�,000 BP (Yokoyama et al., 2000). Climate and associated vegetation changes are considered as the drivers of extinction of lions, and coupled with hunting by early humans in more recent times arguably caused the extinction of tigers as well in Sri Lanka (Manamendra-Arachchi et al., 2005). However, the possibility of their continued existence in refugia on mainland India prior and during the last glacial maxima cannot be ruled out. Though evidence for such claims are yet to be discovered, such possibilities seem realistic and open up a range of questions that are yet to be answered.

The presence of Neolithic/Chalcolithic cave paintings of lions in Bhimbetka rock shelters of central India (30,000�,000 BP Badam and Sathe, 1991) suggest lions to be early entrants into India and lend support to the fossil records from Sri Lanka. But their absence at the peak of the Indus valley civilizations as evidenced from the lack of their appearance in seals, pottery, and terracotta images that abound with representations of other contemporary wildlife like tigers, elephants, and rhinoceros (Divyabhanusinh, 2005) remains a mystery. It is possible that the earlier entrant lions became locally extinct within most/all of India as had happened in Sri Lanka. Lion terracotta art was recovered at Mehrgarh near Bolan Pass (currently in Pakistan), one of the important Neolithic (9,000𠄴,500 BP) archaeological sites and a lion handle was excavated from Taxila (currently in Pakistan) that dated back to late Harappan period (2,500 BP) (Divyabhanusinh, 2005). While depictions of tigers in Harappan art are widely known, a rare find of a two-headed lion like figurine was also recovered from the Indus valley site (Iyer, 1977). The advent of the Aryans and their influence was marked with an increase in the familiarity with lions. It would be difficult to differentiate if this familiarity was because of lions living in India or by Aryans encountering them in Persia during their migration. Ancient Hindu literature, the Rigveda, which is dated between 3,500 and 4,000 BP mentions the word simha (Sanskrit for lion) at least on 15 different occasions. Based on recorded history, Singh (2007) speculates that modern lions entered India through the western passes of the Hindu Kush and occupied most of Northern and Western India between 2,600 and 3,500 BP. Divyabhanusinh (2005) attributes the entry of modern lions in the Western and North-Western parts of India to the loss of tropical forests caused by environmental changes such as prolonged drought (which is also attributed as a cause for the Aryan migration) and habitat modifications caused by anthropogenic factors like clearing of forests for grazing lands and agriculture. About 3,500 BP the tiger seems to have lost its supremacy to the lion, which was prominently depicted in Indian art, culture, sculpture and literature (Iyer, 1977). Subsequently, by the time Jainism and Buddhism evolved, lions were well-established in India. Contemporaneous ancient Jain and Buddhist literature depicted the lion as a symbol of the 24th Jain tirthankar (spiritual leader) Mahaveer (ߢ,600 BP) while Gautam Buddha, the son of the Sakya chieftain (born around 2,500 BP) was known as Sakyasimha after achieving enlightenment. Lion capital at Vaishali during pre-Mauryan era (2,100𠄲,300 BP) symbolized the supreme iconic status of the species as a royal symbol. Lions featured in the ancient Buddhist texts of the Jatakas (ߢ,400 BP) that depict Buddha as various animal incarnations, often as a noble lion (Choskyi, 1988). The lion was ubiquitous as a symbol of royalty and was given a place of pride in lore and text in Sankrit, Tamil, Pali, and Persian. By the time of the Puranas (ߡ,000𠄱,500 BP) and the great epics of the Ramayana and Mahabharata, the lion became the vahana (carrier) of Goddess Durga and was considered an incarnation of God Vishnu as “Narasimha” and thus became a symbol of worship in Hinduism. In modern Republic India the lion was designated as the national animal (Rangarajan, 2013), a status it subsequently lost to the tiger in 1973 (Rangarajan, 2001). Independent India is often depicted as Bharatmata (mother India) riding a full maned lion (Newell, 2011). The 3 rd century BCE Ashoka pillar depicting four lions standing back-to-back, within a Persepolitan style proclaiming the ruler's universal all-encompassing vision of dhamma has now become the national emblem for India and is printed on its currency and official documents. The recent icon adopted by the Indian Government for encouraging local entrepreneurship is a “make-in-India” logo of an Asiatic lion made from mechanized parts.

Enhydra lutris

The term Enhydra comes from the Greek &ldquoen&rdquo (&epsilon&nu) = in and &ldquohydor&rdquo (&upsilon&delta&omicron&rho) = water, therefore, &ldquoin the water&rdquo, due to its habitat lutris is the Latin name of the otter.


In the past this animal occupied a very vast north-Pacific area with a bow going from north of Japan (Hokkaido), through Sakhalin, the Kuril Islands, Kamchatka, Aleutian Islands, southern coast of Alaska and southward up to California, with a very numerous population, of many hundred of thousands of specimens.

The hunting, started by mid of the &lsquo700 has greatly reduced the number of sea otters that in early &lsquo900 was reduced probably to only 2000 individuals.

The hunting stop and the conservation policies have had an extraordinary success and presently it is estimated that 100.000 to 150.000 specimens do live gathered in colonies localized mainly in Russia, Alaska, British Columbia, Washington and California, the first two regions being those hosting the greatest number of animals.

The range occupied goes from the 57 degrees North, where the limit is given by the freezing sea, up to the 22 degrees North, limit of the distribution of the forests of kelp, the main habitat of the sea otter.

Three subspecies are accepted, with different geographic distribution: Enhydra lutris lutris (Linneo, 1758) present in Japan, Kuril Islands, Kamchatka Peninsula and Commander Islands, Enhydra lutris kenyoni (Wilson, 1991), from the Aleutian Islands up to Alaska, to Canada and up to Oregon and Enhydra lutris nereis (Merriam, 1904) present in California.

This species must not be mistaken with the other so-called marine otter (Lontra felina), South American mustelid mainly terrestrial that frequents the estuarine habitats.


The sea otter lives in coastal waters of medium depth (usually, 10-30 m), preferring areas protected from the waves thanks to emerged rocks, coastal barriers and lives especially in the forests of Kelp (Macrocystis pyrifera, laminarias, brown algae).The forests of kelp offer a habitat extremely rich of preys good for the sea otter, invertebrates as well as fishes. The long ribbons of the kelp are also used by the sea otter as anchorage in order to avoid being dragged by the currents while sleeping or feeding.

Squat head, like a marmot, and long sensitive whiskers to find the preys in the torbid waters © Giuseppe Mazza

Since the sea otter lives in the kelp forests, the preferred stretch of sea varies very much depending on the distribution of these algae that in some instances, like in some zones of Alaska, goes up to many miles off the coast. The sea otters appear to prefer habitats where the canopy of the kelp, that is the apical portion of the long fronds, reaches the surface.


The sea otter is the heaviest among the otters and is also the one having the stockier appearance.

The Amazonic Giant otter Pteronura brasiliensis exceeds it in length but not in weight.

The males have a weight from 22 and 45 kg, with a length of 1,2-1,5 m, whilst the females, smaller, weigh 14 to 33 kg, with a length of 1-1,2 m.

The tail is responsible for about one third of the whole length. The Alaskan Northern sea otters, to be attributed to the subspecies kenyoni are slightly bigger than the Californian Southern sea otter, subspecies nereis.
Apart the size, the sexual dimorphism is quite poor.

The front limbs have retractile claws, the fingertips and the palm are glabrous and allow a good grip and a valid sense of touch. The hind feet have webbed digits and their length increases from the first to the fifth one, therefore the big toe is the shortest and the little finger is the most developed. This characteristic produces a hind feet formed like a fin, optimized for swimming.

The head is short and stocky and the muzzle has long sensitive whiskers that help in detecting the preys in torbid waters.

The eyes have a very high power of accomodation, of about 60 diopters, that renders possible a good vision in air as well as in water. Like in the night animals, the rear surface of the retina is reflective (tapetum lucidum) and not black as in the diurnal animals (tapetum nigrum).

Among all mammals, Enhydra lutris is the one with the thickest fur: 100.000-400.000 hairs per It has 2 types of hairs, the upper ones, the guard, that stop the water, and the lowest, thick and thin, the famous wad, that trap the air with an extraordinary thermal insulation: 4 times more than equivalent fat layer © G. Mazza

This characteristic allows a high sensitivity to light, useful for the vision in poorly luminous ambients such as the underwater one, as the light rays, reflected by the tapetum lucidum return to hit the photosensitive cells of the retina practically doubling the sensitivity.

The sense of smell is little known but the turbinates are well developped, suggesting an ample surface of olfactory mucosa, and we know that the males recognize by the smell the females in oestrus and follow their trace in water.

The canines are well developped and the big molars are flattened, with rounded surfaces, suitable for crushing the shells of the crustaceans. The sea otters, unique among carnivores, have 4 inferior incisor teeth (two per side) instead of 6.

Apart the incisors, the Sea otter (Enhydra lutris) is an unusual carnivore with very strong rounded molars done for crashing the sea urchins and the hardest shells © Giuseppe Mazza

Unlike other marine mammals, in the sea otter is very scarce the subcutaneous fat and the defence against the cold is provided by the fur. This is formed by two types of hairs, the protection hairs, or guard hairs, longer and resistant, usually paler, and the lower ones of the underfur, thicker and thinner, usually darker.

The guard hairs, water-proof, protect and keep dry the lower layer that trapping the air, furnishes the thermal insulation. The thermal insulating power of this fur is very high, about four times higher than that of an equivalent layer of adipose tissue.

Among all mammals the sea otter is the one having the thicker fur: 100.000 to 400.000 hairs per square centimetre, and enormous value if we think that in the dog the hairs amount to 1000 to 9000 per square cm and in the man the hairs are 100.000 in the whole head. This helps us in understanding why the fur traders esteemed the sea otters so much!

In the skin of the sea otter are present particular sebaceous glands that secrete a fat substance that increases the water-proof power of the fur, similarly to the secretion of the gland of the uropygium (rump) of the aquatic birds.

The anal glands are absent but are, on the contrary, present in the other mustelids. The sea otters have some skinfolds at the base of the front paws that are utilized as a sort of pockets where to keep their preys or the stones they use as tools.

Closely linked to marine life and dedicated to diving, the sea otter presents a series of morpho-functional adaptations to this style of life, in some cases more evident than those of the pinnipeds and close to those of the cetaceans.

Since the sea otter spends in water most of its time, even when it eats or devotes to the care of the fur and even during the sleep or the delivery, it needs to have a great buoyancy in order not to be obliged to swim continuously for floating. This property is obtained thanks to the thick fur that traps a huge quantity of air and to a great development of the lungs, that furthermore furnish a great quantity of oxygen for the long apneas during the submarine hunting.

Another aspect that favours the long apneas comes from the high capacity of taking advantage of the anaerobic metabolism, that is to get energy from the sugars without needing oxygen. At the time of the dive a series of physiological responses is started aimed to save oxygen. Firstly occurs a slowing of the heart rhythm that from the 125 beats per minute decreases even to 10 pulsations. This allows to reduce the consumption of oxygen by the heart, leaving a greater quantity of it to the other organs.

As the most evolved apes do, the otter has learnt to use tools for getting the food: in this case special stones that takes underwater in the folds of the fur. So it hammers pitiless the poor Haliotis to detach them from the rocks, breaks them, and then emerges for enjoying them in the sun © Giuseppe Mazza

Secondly, a selective vasoconstriction takes place in the peripheral parts of the body, such as the paws and the skin, leaving on the contrary more blood for the heart and the brain.

The muscles continue to be oxygenated in spite of the reduction of the blood flow thanks to their important internal reserves of oxygen. In the muscles of the sea otter, as well as of the other mammals is present a protein, the myoglobin, capable to link the oxygen and then to give it to the muscle when necessary.

Averagely, in the terrestrial mammals the concentration of the myoglobin is of 1 g/100 g muscle, whilst in the sea otter such concentration, and consequently the capacity of storing oxygen, is much higher (3 g/100 g).

In its adapting to the marine life the sea otter must also deal with the problem of the salinity: in fact it feeds on marine invertebrates that have a high contents in salts and drinks sea water with its high concentration of sodium chloride. The diet of the sea otter, furthermore, is very rich of proteins.

All this imposes the need of eliminating through the urines the exceeding salts and the waste products of the proteins metabolism, without anyway losing excessive quantities of water.

The multilobed kidney of the sea otter responds with an extraordinary capacity of concentrating the urines and therefore of saving water although eliminating the exceeding salts and the wastes. We can quantify this effectiveness by considering the concentration of solutes in the urines of the otter, that is more than the double than the sea water and five times more than the human urines.

Hence the sea otter, even if drinking sea water is able to keep the water and to eliminate the salts as well as the waste products of the metabolism.

Ethology-Reproductive Biology

Among all mammals, excepting the cetaceans and the sirens, the sea otter is the one more strictly linked to the aquatic life. Enhydra, though being able to move on the dry, spends most of its time in the water, where it hunts, sleeps, mates, delivers and breeds the pups.

The tail serves as rudder and reaches 100 m of depth with very long apneas. To save oxygen, in immersion the heart slows the beat from 125 to 10 pulses per minute, the blood vessels narrow privileging heart and brain at the cost of the muscles that get the necessary oxygen from special reserves, triple compared to those of the common terrestrial animals. This thanks to a particular protein, the myoglobin, capable to link the oxygen and then to give it to the muscle when necessary © Giuseppe Mazza

When resting or sleeping, the sea otters float on the back, keeping the hind paws out of the water and the front ones bent on the chest or used to cover the eyes and often wrap in the fronds of the kelp to avoid being dragged by the current. When not engaged in hunting the sea otters devote diligently in caring the fur, to maintain its insulation qualities.

Even if it is a mainly diurnal hunter, the sea otter can hunt also during the night. The sea otter swims thanks to wavy dorsoventral movements of the hind part of the body and of the tail, like a seal and a dolphin, thanks to particularly mobile joints. The hind paws and the tail, besides for the propulsion, are utilized to control the direction. Even if are documented maximum dives up to 100 m, usually the sea otters go fishing at lesser depths. A dive lasts from one to four minutes, with depths of usually between the 20 and the 30 metres.

The fore paws have retractile claws and wrinkly and sensitive pads with which take the food to the mouth © Giuseppe Mazza

The preys, that are caught with the fore paws, thanks to the clawed digits and the wrinkly and sensitive fingertips, consist essentially in marine invertebrates, such as sea urchins, molluscs like in particular the rock scallops (Crassadoma gigantea, relative to the Mediterranean scallops), the mussels, the clams and the abalones or ormers (Haliotis), that are often their choice preys, but also cephalopods and crustaceans. The fishes are more rarely preyed and only exceptionally the marine birds.

The extremely powerful rounded molars render possible to break the hardest shells. To open the sea urchins the sea otter breaks the involucre on the oral side, less spiny and then licks the contents.

Possibly only case among the non primate mammals, Enhydra utilizes some tools: the sea otters in fact use stones collected from the bottom to detach the preys from the substratum as well as to break their shell. In some occurrences they slam the prey on a stone they hold on the chest and in other cases, on the contrary, they use the stone for breaking the prey they keep on the chest.

Skinfolds present between the fore legs and the thorax are utilized as pockets where to keep stones and/or preys. The same stone is often utilized for many dives. These animals have also the habit to wash the preys and do this holding the prey against the thorax and then turning over in the water.

Despite not being a social animal, the sea otter often lives in groups of some tens of individuals, however each individual hunts alone or at most in pairs, usually formed by mother and pup. Cases of thefts of preys to other couples have been observed. Conversely, during the rest we can see not structured groups more or less numerous, even of some tens of specimens floating close each other. During the period of the reproduction the male defends its own territory preventing the entrance to other males. The females, more numerous, move freely among the males&rsquo territories. The males that do not have a private territory usually do live in groups.

Happy couple feeding with crustaceans and a squid. Enhydra lutris is not social and the love bond lasts 3 days at most © Giuseppe Mazza

The sea otters communicate essentially through body contact and also through vocalizations, even if they are not animals particularly noisy. The most talkative are the young calling their mothers. Have been described eight different types of vocal emissions but it is not known in which situations they are emitted. Also the sense of smell has an important rôle and seems that each individual has a particular smell that informs about its identity, the sex and the reproductive physiological status. A lot of time is devoted to the accurate maintenance of the fur (grooming) cleaning, combing and aerating especially the lower layer of the thickest and thinnest hairs.

The sea otters are polygynous animals, that is, each animal mates with more females usually the females deliver every year or at times every two.

Also mating occurs in water. Found with smell a female in oestrus, immobilizes it grasping the muzzle with the jaws and completes its mission © Giuseppe Mazza

If the newborn does not survive, the mother may have a new oestrus and mate again during the same year. When a male finds a receptive female the two assume a playful and sometimes also aggressive behaviour. They stay together during the whole period of the oestrus, about three days. During the mating, that occurs in water, the male grasps with the jaws the head or the muzzle of the female. It is not rare to observe females having scars on the muzzle, memory of injuries gotten during the mating.

The pregnancy has a much variable duration, from four to twelve months. This variability of duration of the gestation is due to the fact that in the sea otters occurs the phenomenon of the delayed impantation, or embryonic diapause: after the fecundation the embryo does not implant immediately in the uterus but may stay in a dormancy status for some months. When then the implant will occur the real gestation lasts four months.

The males of Enhydra lutris do not breed the progeny. Unlike what usually happens in the carnivores world, the females of this species have only two udders © Giuseppe Mazza

This a strategy some animals adopt to avoid that the pups are born in unfavourable periods.

Also the delivery takes place in water and comes to life usually only one pup, with a weight of about 1,5-2 kg, that is not able to swim, but its fur holds as much air that allows it to float.

The males do not take part to the breeding of the progeny.

Unlike many carnivores the sea otters have only two udders. The milk has a contents of fats of the 20-25% and the pups are nursed for about 6 months, but already much before they begin to take solid food. In case of danger the females grasp the pup with the jaws and dive.

By the eighth month the young become independent and between the 3 and the 5 years they are sexually mature, the females more precociously than the males.

The average length of life is estimated in 10-12 years, with a maximum reported of 23 years.

Behaviour on the ground

Even if the sea otter spends most of its time in water, it is possible to encounter small groups of animals in the dry, usually on rocks covered by algae. It appears that the stays on the land are more frequent in winter, when the sea is very rough and occur more often in the zones less frequented by the man. The Enhydra is considered by the ecologists as a &ldquokeystone&rdquo species because its presence rules in an important way the abundance of many other species, animals as well as vegetal, therefore its protection represents an important instrument for the control of the coastal marine ecosystem.

The high daily consumption of marine invertebrates by the sea otter renders it a limiting factor of the abundance of the benthic species.A sea otter consumes daily about the 30% of its weight that, for a 25 kg animal means almost 8 kg per day. A population of 5000-8000 specimens like that of the Aleutian Islands means a consumption of about 56 tons per day! In California, in the zones frequented by the sea otters the big sea urchins are absent out from narrow crevices of the rocks where are unreachable for them, whilst they abound where the sea otters are absent.

The pups are milked for 6 months, but long before they begin to assume solid food. One Enhydra consumes daily about the 30% of its weight that, for a 25 kg animal means almost 8 kg per day. Sedentary, has therefore an important habitat impact, controlling for instance the proliferation of sea urchins that menace the sea stars and the great laminarias formations © Giuseppe Mazza

Moreover, by reducing the number of the sea urchins the sea otters facilitate the development of the kelp forest that the sea urchins, proliferating, may damage.

A further positive effect is the protection agains the starfishes whose excessive proliferation is harmful for the seabeds. On the other hand, the taking of species with commercial interest such as the abalones places the otters in competition with the fishermen.

Enhidra lutris is also considered as an indicator of the health state of the marine costal ecosystem.

Being a relatively sedentary animal and at the apex of the food chain, it can store in its organism the contaminants, to which is particularly sensitive.

Nourishing mainly of filtrating invertebrates that accumulate in their tissues the toxins and the microorganisms, the sea otter is particularly damaged by many pollutants, especially those not soluble in water but present in the algae and in the sediment, and by pathogenic microorganisms. An exemplary case is that of the poisonings due to toxins of dinoflagellates.

It is known that some dinoflagellates produce extremely powerful toxins: during the &ldquoblooming&rdquo periods of these microscopic algae the filtering molluscs may accumulate strong quantities of toxins and become toxic for the man and the animals. The sea otter is strongly exposed to this risk and have occurred
widespread deaths of otters due to this phenomenon.

However, it seems that the sea otters are capable to sense the presence of the toxins and in such case they change typology of feeding and, after some observers, even reject some parts of the mollusc more loaded of toxins.

Some studies have proved that the 60% of the death rate of the sea otters in some zones is due to infective diseases linked to urban or agricultural waste.

An example is given by Toxoplasmosis, probably caused by pollution of urban waste with cat faeces, that has caused episodes of mortality in the sea otters in California. Also the protozoan Sarcocystis neurona can cause in the sea otters fatal myeloencephalitis. This protozoan is an intestinal parasite of the Opossum (Didelphis virginiana, final host), that emits the sporocysts with the faeces. The sea otters, who are one of the secondary hosts, may be infested through the faeces introduced in the waters. More common is the problem of the intestinal Acanthocephala Corynosoma of which the sea otters get infested eating infected crustaceans.

Presently Enhydra lutris is considered as an endangered species (CITES appendices Appendix I and II), no longer for hunting but for the dangers coming from the damages to the habitat, especially those linked to the oil pollution or by other sources and the net fishing. It is estimated that the accident of the VLCC Exxon Valdez of 1989, with the oilspill of 50-150.000 cubic metres of crude oil, has caused in Alaska the death of thousands of sea otters and still now the pollution of the area causes damages to the animal populations.

With even 45 of weight, the sea otters males exceed the Amazon giant otter that is only slightly longer © Giuseppe Mazza

The fur of the sea otter is very sensitive to the oil and other contaminants pollution, that facilitating the penetration of the water in the innermost layers of the fur can reduce its insulating capacity and cause hypothermia, pneumonia and death. Also contaminants like the tributyltin, used in the anti-fouling naval paints, insecticides like the DDT (nowadays forbidden), and PCB (polychlorinated biphenyls) have caused and still cause serious damages to this animal.

Apart from the problems of the examplified pathologies, some predators can attack the sea otters and among these we remind the killer whales, the sea lions, and especially the sharks, in particular the Great white shark (Carcharodon carcharias), that is probably the main foe of the sea otters. The young are at times predated by the Bald eagle (Haliaeetus leucocephalus). When on the land, the sea otters may be attacked by the coyotes (Canis lantrans).

Apart cetaceans and sirenids, Enhydra lutris is the mammal more linked to water © G. Mazza

Relations with man

The sea otter was described in 1741 by Georg Steller, German physician, zoologist and explorer, membre of the expedition of Vitus Bering who, on Russia&rsquos account, was exploring the Arctic seas. In the sinking of the ship &ldquoSt. Peter&rdquo died most of the crew, among them also Bering (or, maybe, Bering died later on from scurvy). Steller was one of the survivors and in the Avacha Island, nowadays called Bering Island, where he had found refuge, he saw the first sea otters (and killed about a thousand of them).

Concerning the abundance of the sea otters and of their lack of fear towards the humans, Steller writes: &ldquoThere were so many of them that we had not enough hands for killing them, whole herds covered the shore &hellip At the beginning they were not afraid of the man, and did not move at our passage&hellipwe killed more than eight hundred of them and, should not have been so small our boat, we could have caught the triple of them&rdquo.

The man has devoted to hunt the sea otters since thousands of years, attracted by the quality of the fur but the taking for centuries has maintained modest. Since when Steller and the shipwrecked survivors of Bering&rsquos expedition took to Russia the skins of the sea otters they had hunted and sold them at high price (10 or 20 times the cost of the precious sable), the fur traders set off the hunt that led to the slaughter of more than one million of specimens. After the Russians started the hunt the Spaniards of California and then the Americans of the coastal regions of the North-West and the Japanese.

When the species was on the brink of the extinction, Russia, Japan, United Kingdom and USA, in 1911, decided to stop the hunting. As we have seen, the vitality of the species has allowed, in the space of 150 years, to bring the numbers to values probably similar to those of a time. Despite the success of this intervention the dangers are not finished, for the previously mentioned reasons and this is proved by the fact that in various populations of Enhydra have occurred during the recent years worrying fluctuations in the number.

Besides the fur, some natives of the coasts frequented by the sea otter did hunt them for the meat. Some travelers describe its taste as loathsome (but better than that of the seals), after the explorers however many of the natives did not agree with this and ate the meats even without salt and littler cooked.

Also the shipwrecked survivors had not many prejudices about the taste and for Steller and his companions the sea otters have been the main food after the wreckage, with particular fondness for the flesh of the females and the pups.

Man represents always their main foe, also after the prohibition of hunting: accidental catching by nets and by fishing lines and wounds caused by the propellers of vessel add their effects to those of the pollution and of the destruction of the habitat.

When resting or sleeping the sea otters float on the back, keeping the hind paws out of the water and the fore ones folded on the chest or on the eyes filtering the light. So as not to drift thet often grasp, as if they were anchors, the robust floating laminary algae. Man represents always their main foe, also after the prohibition of hunting © Giuseppe Mazza

The populations of the natives in contact with the sea otter have created myths and traditions linked to this animal. As an example we cite a tale of the Aleutian Islands concerning the origins of the sea otter: &ldquoOnce upon a time there was a nice girl who with her brother lived in a village close to the reef, where lived the powerful Spirit of the North. One day the Spirit kidnapped the girl to marry her and she was standing all alone and scared till when, on a nice day, the brother was able to free her and take her back home. The Spirit, enraged, wanted to destroy the village and so caused a terrible storm and the inhabitants, terrified, drove out the two young. These went to seek refuge on the beach, but a huge wave dragged them into the sea. By sure they would have drowned but the Goddess of the sea, moved to pity, transformed them in two nice sea creatures, giving them, as a gift, the most wonderful fur, that would protect them against the cold even in the most frozen ocean. Thus were born the sea otters.&rdquo

Mustela lutris (Linnaeus, 1758), Latax lutris (Merriam, 1904).

Related Species

North Pacific Right Whale

Southern Right Whale

Humpback Whale

Bowhead Whale

Research and Technology

Studying sea turtles is a difficult task as these animals spend almost the entirety of their lives beneath the ocean surface. It is mostly hatchlings and nesting females that spend any portion on land. In fact, the period of time in between hatchlings making their way into the surf and when they return to nest as adults is often called a sea turtle’s “lost years.” Scientists do not really know much about where they go and what they do. As technology has improved over the years, researchers have been able to observe some of the mysterious undertakings of turtles at sea, but we are far from having all the answers.

One tool that has helped in the quest to unlock the secrets of sea turtles is the National Geographic Crittercams program. Cameras have been attached to various animals to give viewers video footage from the perspective of the animal. Sea turtles have successfully had Crittercams attached, allowing us to see videos captured from the backs of sea turtles. Footage has shown them foraging for food, swimming, diving, and interacting with other turtles.

Satellite tags can track sea turtles like never before, helping with research on where newly hatched sea turtles go and how different populations hunt. (Jake Levenson)

Researchers can also track sea turtle movements and habits using satellite telemetry. Electronic tags are attached to sea turtles and their signals tracked using Earth-orbiting satellites. The tags transmit data which is received by a satellite when the host sea turtle emerges from dives to the ocean surface. The satellite then sends the data to researchers’ computers. The tags’ data collecting capability usually lasts from 6 to 10 months. These data can tell us important information such as where and when the animals move, the timing and depth of dives, body temperature, and how long the sea turtle spends beneath the surface in between breaths.

Other types of tags include flipper tags and passive integrated transponder (PIT) tags. Flipper tags are external tags attached to a sea turtle’s flipper. They are generally made of metal or plastic and have an embossed number unique to the individual sea turtle. PIT tags are internal and when scanned, they transmit information stored in the individualized barcode, the equivalent of an animal’s individual fingerprint. Flipper and PIT tags can be used to observe an individual sea turtle’s movements over time. Unlike satellite telemetry tags, they cannot give detailed behavioral and physiological data such as the depth of dives or internal vital signs.


I particularly appreciate the useful comments from my colleagues, Prof. Lynette Hart (Veterinary Medicine), Richard Coss (Psychology) and Lynne Isbell (Anthropology) of U. Davis as well as an anonymous reviewer and, especially, the editor of this special issue. Research cited in this review by the author was supported by grants from the US National Institutes of Health and the National Science Foundation. Preparation of the review was supported by the UC Davis Centre for Companion Animal Health (allocation no. 03-65-F).

Episode 3: Cougar M198


Narrator: This is Dan Stahler. And—I swear—Dan Stahler practically has fur in his blood. He studies wolves and elk…He’s the endangered species coordinator for Yellowstone National Park. And he’s the project lead for Yellowstone’s research on mountain lions—also called pumas or cougars—And last year, Dan and his team had a cougar mystery to solve.

Dan Stahler: All right, Good Morning. It’s January 28th. Dan Stahler, Colby Anton, Nathan Varley heading on in to the Black Canyon of the Yellowstone to go investigate on our only cougar collared right now, M198. He’s a 3-year-old male. We’re gonna go check it out and see what we see.

Narrator: First, a little background here on M198. The M stands for male and 198 is his identifying number. M198’s collar that Dan was talking about is very high tech. Dan Stahler: sort of FitBits if you will for cougars One of the things those collars can do is communicate with a satellite system to record the cat’s location on the landscape every 3 hours. Dan could log in on a computer, look at all those location points and see where M198 had been. Dan Stahler: We used those points to identify clusters on the landscape where he spent time. Then usually about a week after he was in that area we would go investigate. Narrator: Investigating the places where cougars have spent time turns out to be incredibly valuable. And it’s a little like a crime scene investigation that you see on TV. Dan and his team can comb the area for DNA, like hair and scat, to help identify individual cats … like how many are out there and who’s who. This non-invasive technique of getting at the demographics of a cougar population is a powerful tool for studying such secretive animals. Or, let’s say a cougar made a kill in that spot. And if so, was it a deer or an elk or a marmot… how old was the animal… was it healthy…how many animals did the cougar kill over a given period of time… these things tell scientists a lot about the food habits of cougars like M198 AND what their impacts might be on populations of prey species like deer or elk. Dan Stahler: We found where he’d killed an adult cow elk. It was the only animal he fed on for 20-some odd days. And that’s kinda typical of a male cougar. They can go a long time without feeding. They’ll make a kill, feed on it, then do their other cougar things and roam around. If the cat stops roaming around – if it stops moving altogether, then the collar sends Dan an alert. For M198, that alert meant that either the collar came off somehow, or it stopped moving because M198 was probably dead. And Dan and Colby and Nathan needed to figure that out. The problem was that the collar suddenly stopped transmitting GPS locations. So finding it was going to take a little work.

Dan Stahler: Colby, it’s too bad we don’t have a more recent track on him, Colby. He’s either down low or he’s tucked in a rock in the boulder field which let’s hope isn’t the case. Who knows Colby, we might get lucky. Narrator: Let’s just say that they didn’t get lucky. M198 had made his way into what Dan calls the Promontory. It’s a gnarly boulder field with rocks the size of cars. Dan Stahler: There are lots of places a kitty could tuck away up here. Narrator: This explains why Dan and his team were unable to get GPS coordinates from M198’s collar. There was no way a collar could communicate with the satellites in outer space through that huge pile of rocks. But those collars also come equipped with radio telemetry. And because the radio beacon transmits its signal directly to Dan’s handheld receiver, he could use THAT to zero in on M198. And the way that works: The closer Dan gets to the collar, the louder the blips -- the radio signal.

Dan Stahler: OK we’re getting closer guys.

Dan Stahler: It’s kind of a fun process because you try to read the signal but think about what the cat would do—how he would move through here. I don’t know they ARE cats. They do amazing things. It would be nothing for him to bounce through this boulder field, but you’d think he’d take a path that would be a little easier on him.

Dan Stahler: OK I think I see some blood up ahead. I don’t know for sure. Yeah….I see where birds or something pecked at blood in the snow.

Dan Stahler: Lot of tracks. He’s in there somewhere. Clicking in real nice on the telemetry now. It’s interesting. Something dramatic went on here. Because there’s blood all over the rocks…look at the stain on that lichen right there…there’s a bunch of cat hair stuck to the rock….

Dan Stahler: Wow. There’s caves all over the place in here….Wow. There’s blood way down. Holy smokes. Hey might be WAY down in here guys.

Dan Stahler: Uh this is a pretty…well…(grunting)…a little spelunking! I didn’t think I’d be doing THIS today.

Dan Stahler: Let’s hope he’s dead and not a wounded cat that’s not happy to see me.

Narrator: Twenty feet under the earth, tracking a bloody cat, Dan and Nathat started to piece together a story of what might have happened to M198.

Nathan Varley (talking to Dan): Did he get pinned in there by a bigger cat? Dan Stahler: Yeah bigger cat, maybe… Nathan Varley: …and they’re fighting…that’s nasty. Dan Stahler: That’s how toms die often. Nathan Varley: Lions are lions. They’re just so powerful Dan Stahler: And you know he’s a 3-year-old tom and was probably trying to establish himself in here and all it takes is one bigger tom to say nuh-uh. Dan Stahler: We’ll know. You know they crunch the skull… Nathan Varley: Oh wow. Brutal. Dan Stahler: …when they kill each other. I think we’ll see it in his head. Dan Stahler: Well, you know, he has an accelerometer collar. So we can look at the activity. We can look at the movements. We might even see signs of a chase taking place somewhere else once we get the data back from it. Nathan Varley: So like, ‘he ran over here and this is where the other cat caught up to him and pinned him in the rocks…” Dan Stahler: Mmmm Hmmmm Nathan Varley: That’d be pretty interesting, wouldn’t it? Dan Stahler: Yup Nathan Varley: That’d be really interesting…How ‘bout that? Dan Stahler: Yeah, like, what are the energetics of a cougar fight? Narrator: OK this is where the idea of the cougar FitBit really comes in. Scientists can use the information from accelerometer collars to understand a lot more about animal behavior and energetics – basically, how much energy it takes for an animal to live its life. This is pretty cutting edge stuff. Dan Stahler: So, our ability to study carnivores like cougars is changing all the time. We take advantage of new technologies that become available…And those of us who have iPhones or FitBits or any activity exercise monitoring machine, may have heard the term accelerometer because they’re all built to these devices. These collars have built in accelerometers that continuously measure the 3-D axis--the neck position--of the cat wearing the collar. So when the animal is walking or resting or pouncing on prey it will record a specific type of activity pattern This data has been calibrated with captive animals--captive cougars--wearing collars on a treadmill, jumping and pouncing on a training course … measuring how much oxygen they’re consuming and that translates to calories burned… Narrator: Calories in. Calories burned. This is the basis of energetics. Dan is collaborating with Colby Anton, a PhD candidate at UC Santa Cruz, on the energetics research. Dan says they will be able to link the data from the captive cougars to the wild cougars in Yellowstone. And biologists in the park have these same collars on wolves. Dan Stahler: …so we can compare the energetics of a stalking carnivore that lives mostly by itself – the cougar – compared to a group-living carnivore that chases after its prey – the wolf – and can see different patterns in their energetics that may have been shaped through evolution, might be shaped by current environmental conditions Narrator: Understanding how these animals respond to environmental conditions, how they survive…what they eat…where they go…how they affect each other and their prey… All of this goes beyond just understanding cougars or wolves. Dan Stahler: It’s really about understanding how the ecosystem works. I think those of us who work with these animals don’t think of ourselves as a wolf biologist or an elk biologist or a cougar biologist. We’re ecologists trying to understand the pieces that make this ecosystem function the way it does. Really, what we’re trying to do is understand Yellowstone—it’s importance to the world, its importance to science …to nature—through the lens of wolves and cougars and elk. So these collars have opened up that world in a much more accurate way. Narrator: And because they want to interfere with the lives of wild cougars as little as possible, Dan and Colby only fit a couple of cats with those collars. Which made M198’s even more important to get back.

Dan Stahler: OK, hey I’m gonna listen to the telemetry.

Dan Stahler: It’s 12:07. Don’t tell me that beacon turned off.

Dan Stahler: That should not have shut off…(sighs) I don’t hear it Colby… Narrator: Despite continuing the search through the caverns without the signal, Dan and Colby and Nathan could not. Find. The cat. Dan Stahler: That pisses me off…. I hate leaving here without this cat and knowing the end of this story. ¬ Dan Stahler: Damn it, Colby . Colby Anton: beacon. Dan Stahler: Pffft…Another typical day in wildlife biology.

Narrator: I think most scientists will tell you that dealing with frustration and overcoming setbacks is something scientists get comfortable with pretty quickly. In fact Dan tells me that a few days later, they were back in that boulder field. Dan Stahler: …and that’s what we did we went back into the area and it was another frustrating search… …And then there was one little spot where I noticed some hair stuck to the top of the rock a little bit of blood and it was just another little slit I the rock that I wasn’t able to catch before…

Dan Stahler: …I squeezed through it…

Dan Stahler: …and I looked down with the headlamp and… Dan Stahler: Definitely not moving. (Sighs) Here he is. Aww. 198. Damn it. So, here I am down in the lions den with 198. He is dead. He’s lying on his side. Blood all over him. Hard to say what happened here but it does look like he’s been attacked. Wow. He must have been beat up pretty good to come down here like that. Bummer. Hard to loose a cat like that. He was the 1st one of the study—but certainly we’ll learn something about him from this event, too (sighs).

Narrator: M198 the very first Yellowstone cougar to contribute accelerometer data to the study. But maybe what’s even cooler, is that he is one of only two wild cougars in the world to have his entire genome sequenced. And this has implications for big cat research worldwide.

Narrator: Back in his office, Dan talked about the death of M198. The necropsy revealed the cat was indeed killed by another cougar. Narrator off mic: And he was your first… Dan Stahler: It was very discouraging. But at the same time, you know, you appreciate the wildness of Yellowstone and the lives these animals live …

…There are relatively few places where you can understand how all these carnivores coexist, compete, interact, and what those impacts may be on prey, scavengers or each other… Narrator: And you know, Yellowstone is pretty special that way. Thanks to focused efforts of native species restoration, the park is more carnivore-rich today than it’s been in over 100 years. Dan says that ecologically, this is great news because carnivores like cougars have a critical role to play. Dan Stahler: Cougars, like other top carnivores through the act of predation, which is a powerful ecological force, they have the capacity to shape and structure ecosystems. Narrator: But from a human-dimensions standpoint, things are still a little thorny when it comes to these top predators. Dan Stahler: If you look at carnivores in particular they have a long history of persecution… Narrator off mic: Where do you think that comes from? Dan Stahler: We have a long evolutionary history with carnivores. Our ancestors competed with them for space, for food…And so it’s probably very much built in to our brains…and it’s hard to shed that baggage that was probably shaped over eons of time…But even today there are still challenges living with carnivores. If you raise livestock, carnivores can be a threat to your way of life. If you’re a hunter, you might find that carnivores compete with you for areas on the landscape that you like to hunt. And for others, they embrace the fact that we live in a place today where we can hunt and recreate and still be in a place where there are carnivores. I certainly feel that way living here at the gateway to Yellowstone in Gardiner MT. It’s a privilege to be able to live in a place where we have so much… Narrator: It’s a place where natural processes--like a cougar fight to the death--still play out. And although it was hard to lose him, the ghost of M198 lives on – inside the larger context of what we know about cougars in Yellowstone. M198 had a story to tell. But there are other cats on this landscape and they have their own stories.

Dan Stahler: We just finished picking up M198 and we have tracks on at least mom and one or two probably big kittens or yearlings…and we’re looking in the snow here and you can see here where the young ones were romping and chasing each other. Colby found a good bed site over here so he’s taking his forceps and collecting the hairs and putting them in a sample envelope hoping we get some follicles on the hair for genotyping the DNA of one of these little buggers.

Dan Stahler: So we’re just leaving the site where Colby got some hairs and lo and behold a nice fresh scat…one of the yearlings, probably…they were goofing around in here….

Watch the video: Carnivores ice age all death scenes (August 2022).