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Posts Tagged ‘mammal’

Giant panda (thanks to Marit & Toomas Hinnosaar) The giant panda (Ailuropoda melanoleuca) is one of conservation’s icons, but these bears are secretive and their ecological needs are not well understood. Scientists have long known that panda populations are strongly associated with bamboo (no surprise, as bamboo is the only food that giant pandas eat); however, new analysis of a large dataset of giant panda habitat-use has shown that they also prefer old-growth forest. In fact, after bamboo, old forest is their second strongest habitat association, and this preference is substantially stronger than their link with other factors previously deemed important for pandas, such as slope, canopy cover, and altitude.

Knowledge of an animal’s habitat requirements is vital to ensure that preserved areas, such as nature reserves, contain sufficient correct habitat to allow a sustainable population to survive. This research demonstrates that secondary forest (forest that has been felled and then allowed to grow back) is not equal to pristine forest when viewed by a panda, and that primary forest is essential to the continued conservation of the giant panda.

Reference

Zhang Z et al. 2011. Old-growth forest is what giant pandas really need. Biology Letters 10.1098/rsbl.2010.1081

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Killer whales (Orcinus orca), or ‘orcas’, are the largest member of the dolphin family. Like all whales and dolphins, orcas are mammals – they breathe air, and mothers produce milk for their live-born young.

Killer whale mother and calf (photo by Sam)Killer whales were originally thought to solely eat fish but, increasingly, research is demonstrating that killer whales in different populations specialise in different prey – and that these populations may even be distinct enough to be separate species.  For example, in the northeast Pacific, off the coast of the USA and Canada, three distinct populations have been observed: the resident population lives close to the shore year-round, feeding only on fish (usually salmon). A transient population moves in and out of the area – these feed on marine mammals such as seal lions and other whales. The third, offshore, population are less well-known but researchers have recently found evidence that they may be specialist shark eaters, preying on Pacific sleeper sharks. These populations act differently to each other, make different vocalisations, and do not interbreed. Similarly in Antarctica, populations specialise on fish, or seals, or minke whales, with some observed hunting penguins.

Killer whales have different strategies for each prey, probably learned from other members of their group (called a ‘pod’). Those hunting seals among the ice of Antarctica will coordinate their swimming into a rush towards an ice floe, creating a bow-wave that can knock a seal off the floe and into the water where it can be caught. 

Other seal hunting pods risk stranding themselves as they launch onto a seal colony’s beach in an attempt to grab an unwary seal close to the ocean edge.

Those populations that hunt other whales, however, will stop using echolocation, which could alert their prey to their presence, while they stalk their prey, and (once caught up to the prey) will harry mother and calf pairs to exhaust the calf, before separating the calf from the help of its mother and then swimming on top of the calf to drown it. 

Killer whales are extremely intelligent predators and their behavioural repertoire is intriguing; I look forward to marine biologists unveiling more of their lives.

References

Ford JKB et al. 2011. Shark predation and tooth wear in a population of northeastern Pacific killer whales. Aquatic Biology 11: 213-224

Morell V. 2011. Killer whales earn their name. Science 331: 274-276

Morin PA et al. 2010. Complete mitochondrial genome phylogeographic analysis of killer whales (Orcinus orca) indicates multiple species. Genome Research 20: 908-916

Further Information

MarineBio

Smithsonian Ocean Portal

Convention on Migratory Species

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African wild dog, South Africa (by Sam)African wild dogs Lycaon pictus are considered one of Africa’s most endangered carnivores, with only an estimated 5000 remaining in the wild (1). Although historically present across most of sub-Saharan Africa, wild dogs now have viable populations in only a few remaining African countries (2, 3) and are considered endangered by the IUCN.

As their name suggests, wild dogs are members of the Canidae, or dog, family, although they are a separate evolutionary line to all other canid species that survive today and are, therefore, the only surviving members of ‘Lycaon’. They are not in any way feral domestic dogs (Canis lupus familiaris) but are a completely different species, and behaviourally similar to wolves (Canis lupus). Their Latin name Lycaon pictus means ‘painted wolf’, and each dog is indeed a riot of tan, black, white and yellow blotches in a pattern unique to each individual.

Wild dog coat - each is individual

Wild dog coat - each is individual

Wild dogs are social carnivores, usually living in packs of 4-20 individuals (4), in which only the alpha (top-ranking) male and female breed, producing up to 21 pups yearly (5). Other pack members help raise the pups, to whom they are usually related (6, 7). Due to this need for helpers, and other important factors (discussed below), 4-6 adult dogs are usually needed to form a pack that can breed successfully (8, 9). When packs get large, a sub-group of one sex will break away (termed ‘dispersal’). When this sub-group meets another dispersing group of the opposite sex, a new pack can be formed (10).

Wild dog packs are nomadic and inhabit vast home ranges of between 250 and 2000 sq km at very low densities of 2-35 dogs/1000 sq km (6, 7). Eight packs are considered minimal for long-term viability, leaving few reserves in Africa large enough to hold sustainable wild dog populations (11). Consequently many reserve populations may have to be managed as part of a metapopulation in the future, with translocations between parks, and also captive packs, to maintain genetic diversity and avoid inbreeding and other problems of small populations (2).

Male impala - wild dog prey (by Sam)

Male impala - wild dog prey (by Sam)

Wild dogs are crepuscular (3), which means they are active at dawn and dusk. They hunt as a pack usually eating small-medium antelope, in particular impala (12), which they ‘course’, running after the prey until it drops from exhaustion – a hunting style also used by wolves. Wild dogs are actually extremely efficient hunters, with a significantly higher hunt success rate than both lions and leopards.

African wild dogs are threatened by diseases such as rabies and canine distemper that spread quickly through a pack due to their greeting behaviour of licking each other’s mouths, and can wipe out entire packs. In addition, because they live at such low population densities, wild dogs require vast reserves to be fully protected and to stop them ranging outside the protected area; for example Selous Game Reserve in Tanzania is 43,000 sq km [approx the size of Switzerland] but only contains around 800 wild dogs (13). Once outside the reserve the dogs can be shot and poisoned by humans who often view them as pests or as potential predators of livestock.

 

Why do African wild dogs live in packs?African wild dog (by Sam)

African wild dogs are obligate co-operators – meaning they have to live in packs to survive and breed successfully. Several factors have been found to influence the difference in survival between large and small size packs. These include:

1) Hunting success – this increases as adult pack size increases due to an increased number of animals killed simultaneously, a decrease in the chase distance of the hunt (using less energy), and an increase in prey range as a large pack enables larger, previously unobtainable, prey to be brought down successfully (9, 14, 15; but see 16).

2) Kleptoparasitism – kleptoparasitism is the stealing of food by another animal. Wild dogs are considerably smaller than lions, leopards and spotted hyaenas and these larger predators will steal wild dog kills if they can – after all, it saves them the energy and effort of catching the prey themselves. Larger wild dog packs can defend their kills more successfully and reduce kleptoparasitism by other carnivores (14).

3) Higher pup survival – larger packs raise more offspring by three main methods a) being able to leave behind a ‘babysitter’ while the rest of the adults go hunting, who can protect or move vulnerable pups, b) by mobbing larger predators, forcing them to leave (other predators, such as lion, leopard and hyaena are a significant cause of pup deaths), and c) by sharing the stress of regurgitation to pups between more adult individuals (once pups are weaned, wild dogs feed them by returning to the den after a hunt and regurgitating the meat they have recently eaten for the pups to eat) (6, 9).

4) Vigilance – larger packs have more eyes and so are more vigilant, enabling them to spot other predators more quickly. This could potentially decrease lion mortality (17), which is responsible for up to 50% of adult wild dog deaths and a large proportion of pup deaths (4).

5) Territory defence – larger packs are more successful at defending their territories; for example, in Selous Game Reserve, Tanzania, 10 out of 10 pack disputes seen were won by the larger pack (4).

 

Further info:

IUCN Canid Specialist Group – http://www.canids.org/species/Lycaon_pictus.htm

 

References

1. Fanshawe JH, Frame LH & Ginsberg JR. 1991. ‘The wild dog – Africa’s vanishing carnivore.’ Oryx 25: 137-146

2. Woodroffe R & Ginsberg JR. 1997. ‘The role of captive breeding and reintroduction in wild dog conservation.’ In: African wild dog status survey and action plan (R Woodroffe, J Ginsberg & D Macdonald eds). IUCN/SSC Canid Specialist Group, IUCN Gland, Switzerland. Chapter 7

3. Creel S & Creel NM. 1998. ‘Six ecological factors that may limit African wild dogs Lycaon pictus.’ Animal Conservation 1: 1-9

4. Creel S & Creel NM. 1996. ‘Limitation of African wild dogs by competition with larger carnivores.’ Conservation Biology 10: 526-538

5. Smithers RHN. 1992. ‘Land mammals of southern Africa – a field guide.’ 2nd Ed. University of Pretoria, South Africa p110

6. Malcolm JR & Marten K. 1982. ‘Natural selection and the communal rearing of pups in African wild dogs (Lycaon pictus).’ Behavioral Ecology and Sociobiology 10: 1-13

7. Girman DJ, Mills MGL, Geffen E & Wayne RK. ‘A molecular genetic analysis of social structure, dispersal, and interpack relationships of the African wild dog (Lycaon pictus).’ Behavioural Ecology and Sociobiology 40: 197-198

8. Estes RD & Goddard J. 1967. ‘Prey selection and hunting behavior of the African wild dog.’ Journal of Wildlife Management 31: 52-70

9. Creel S & Creel NM. 2002. ‘The African wild dog: behavior, ecology and conservation.’ Princeton University Press, New Jersey

10. McNutt JW. 1996. ‘Sex-biased dispersal in African wild dogs Lycaon pictus.’ Animal Behaviour 52: 1067-1077

11. Hofmeyr M. 2001. ‘Introduction of the African wild dog (Lycaon pictus) to game reserves.’ Proceedings of a symposium on the re-introduction of larger mammals to game reserves October 2001. Onderstepoort, South Africa

12. Owen-Smith N & Mills MGL. 2008. ‘Predator-prey size relationships in an African large-mammal food web.’ Journal of Animal Ecology 77:173-183

13. IUCN Canid Specialist Group: http://www.canids.org/species/Lycaon_pictus.htm. Accessed Sept 2010.

14. Fanshawe JH & Fitzgibbon DC. 1993. ‘Factors influencing the hunting success of an African wild dog pack.’ Animal Behaviour 45: 479-490

15. Creel S & Creel NM. 1995. ‘Communal hunting and pack size in African wild dogs, Lycaon pictus.’ Animal Behaviour 50: 1325-1339

16. Carbone C, Du Toit JT & Gordon IJ. 1997. ‘Feeding success in African wild dogs: does kleptoparasitism by spotted hyaenas influence hunting group size?’ Journal of Animal Ecology 66: 318-326

17. McNutt JW. 1996. ‘Adoption in African wild dogs, Lycaon pictus.’ Journal of Zoology, London 240: 163-173

Information correct at 23.09.2010

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The ‘photo of the fortnight’ is any animal photo I’ve spotted recently that I like the look of… and I obviously had to kick off this section with one of my own photos – yep; it’s biased, but I’m going to do it anyway!

African elephant herd taking the low road

This is an African elephant herd in South Africa. African elephants live in same-sex herds – this is a group of females and calves, who will be led by an old female termed the ‘matriarch’. Males live in bachelor herds, although older males of mating-age can be a bit bad-tempered so often live on their own!

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