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Archive for March, 2011

Asian elephant (thanks to Kabacchi)Behaviourally, wild elephants perform many actions that suggest cooperation among their herd, such as looking after other mothers’ calves, helping herd members out of mud and other sticky situations, and collectively protecting the herd’s calves against predator attacks. Proving elephants cooperate with each other experimentally, however, is difficult – not least because elephants are huge and potentially dangerous animals to be doing experiments with!

In this week’s PNAS, Joshua Plotnik and his fellow researchers devised a clever experiment with Asian elephants, Elephas maximus, at the Thai Elephant Convservation Center. Adapting a test previously used with chimpanzees, the researchers provided pairs of elephants with a challenge – a table with food on it lay behind a net just out of the elephants’ reach, but a rope had been curled around the table and one end of this rope lay in front of each elephant. If just one elephant pulled their rope end, the rope pulled free of the table and so neither elephant got the food, however, if both elephants pulled their rope simultaneously, the table was pulled towards them and they were rewarded by being able to reach the food.

The research demonstrated that not only did the elephants quickly learn this task, they also learned to wait by their rope for their partner to be released before pulling on the rope (up to 45 seconds after their own release and access to the rope).  In addition, two elephants devised their own method for getting the food; one would wait for his partner to be released – but he waited by the partner elephant not by the experimental apparatus. The second worked out that she could stand on her end of the rope and the other elephant would then do all the pulling!  Finally, in control trials, where one elephant’s rope was out of their reach (i.e. the task was impossible), the elephants gave up before, or soon after, their partner gave up, suggesting that they recognised it was their partner and not just tension on the rope that they required to complete the task.

Although this behaviour perhaps does not sound that impressive to us humans, it is in fact pretty unusual for the animal kingdom. Humans are masters of cooperation with peers, but most other animals cannot coordinate their behaviour to work as a team to gain a reward (examples of animals that can include apes, dolphins, and domestic dogs). In similar experiments to this, for example, rooks (Corvus frugilegus) did not wait for their partner if the partner’s release was delayed. The elephants’ ability to learn this type and level of cooperation between two individuals, therefore, puts their cooperation skill level on a par with chimpanzees.

Reference

JM Plotnik, R Lair, W Suphachoksahakun, FBM de Waal. 2011. Elephants know when they need a helping trunk in a cooperative task. PNAS 108(12): 5116-5121

Further Information

Asian elephants:
The Encylopedia of the Earth
WWF
National Geographic

Cooperative behaviour:
Game theory and the Prisoner’s Dilemma
Cooperative behaviour meshes with evolutionary theory – SciencDaily
How did cooperative behaviour evolve? – Science 

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Squid (not the correct species, but gives you an idea! Thanks to Dan Hershman)In order to survive, prey species need to use different tactics to put-off or escape from predators with different hunting techniques, and recent research has demonstrated that longfin inshore squid, Loligo pealeii, do exactly that.

Staudinger et al analysed experimental predator-prey trials filmed in an indoor research tank between squid and bluefish (Pomatomus saltatrix; 35 trials; 86 interactions) and squid and flounder (Paralichthys dentatus; 29 trials; 92 interactions). Squid are prey for many species of fish, mammals and seabirds and are soft-bodied without the defence of shells, spines, or stinging cells. They, therefore, have evolved a wide range of defence behaviours including the ability to change colour in order to camouflage with their background, and the squirting of ink while fleeing to confuse predators, but the researchers wanted to know whether these behaviours consistently differed depending on the type of threat.

In the trials where squid were confronted with bluefish, which actively swim around in a school (group) hunting for their prey, the squid were more likely initially to use a ‘stay’ response (69%, 59/86 interactions) such as dropping to the bottom of the pool while changing their colour to camouflage against the floor’s gravel and sand substrate. The squid would then remain motionless on the pool bottom unless a bluefish demonstrated it had spotted them by orientating into an attacking posture, upon which the squid would switch to a ‘flee’ behaviour such as flight or inking and fleeing.

Flounder (thanks to jurvetson)When attacked by the ambush predator flounder, which hid in the tank substrate, however, squid less rarely used ‘stay’ tactics (20%, 17/92 and never dropped to the floor to camouflage themselves. Instead the squid switched to ‘flee’ as their most frequent initial response to a flounder attack (44%, 40/92 attacks), using various ‘flee’ strategies including the group of squid scattering in multiple directions,  and a blanch-ink-jet behaviour (where the squid turned transparent, ejected an ink cloud and then jetted away from the threat).

The two different initial responses to bluefish and flounder were statistically significant behavioural differences, demonstrating that the squid recognised the danger posed by each predatory species and took different avoidance action depending on the type of threat.

Squid (thanks to icelight)Although further research needs to be done to ascertain whether these squid anti-predator responses are species-specific (i.e. to bluefish and flounder) or more general (i.e. the response is similarly divided for all ambush and all cruising predators), this paper is an interesting start to deciphering the complexities of the longfin squid’s predator responses.

Reference

MD Staudinger, RT Hanlon, F Juanes. 2011. Primary and secondary defences of squid to cruising and ambush fish predators: variable tactics and their survival value. Animal Behaviour 81: 585-594.

Further Info

– Wikipedia – Longfin inshore squid
Animal diversity web
Marine biological laboratory  

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This fortnight’s highlight is a collection of photos by the Smithsonian Institute taken by scientists using camera-traps. Camera-traps are an important tool in zoology research nowadays. Essentially a camera-trap is an infra-red (or, less usually, pressure pad) triggered camera (sometimes pair of cameras) set up across a trail or at a place where the target animal is likely to pass (such as a scent-marking point, salt lick, or waterhole) that takes a photo automatically when an animal breaks the infra-red beam (or stands on the pressure pad). They allow scientists to see rare and cryptic (camouflaged) animals, to make population estimations of animals in dense habitat such as rainforests where you don’t usually see the animals, and to prove that certain species are present or using particular habitats. And as a nice bonus, you get some interesting and beautiful photos of some of the rarer and more secretive animals on our planet.

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