Behavior Brief

Rodents replace mastodons

Credit: FLICKR CREATIVE COMMONS, BRIAN GRATWICKE

The gigantic seeds of the black palm tree of Panama used to be dispersed far and wide by elephant-like creatures such as the mastodon, but since these animals went extinct 10,000 years ago, the tree's survival has been a mystery. Now, the results of a year-long study, published July 16 in Proceedings of the National Academy of Sciences, reveal that small rodents have taken over the job by stealing from their neighbors. Rainforest rodents known as agoutis bury the seeds like squirrels do with acorns, but thieving between individuals is rife. Transmitters attached to 589 seeds sent a signal every time they were dug up and reburied, and after just one week, every seed had been dug up at least once. One seed followed in the study was stolen and transported to a new hiding place 36 times, in the end traveling a total of 280 meters— as far as a mastodon might have. Many of the seeds were thus moved far away from the mother tree, allowing less competition and favorable conditions for germination.

Researchers also tagged the agoutis and set up camera traps to catch them in the act, and the success of the operation led co-author Roland Kays to suggest in a press release that such sophisticated techniques could be used "to study how animals can help trees adjust to climate change through seed dispersal.”

It's not just lunch

People are more jealous of their partner having a meal with an ex-lover than interacting by email, phone, or having a coffee, researchers report this month (July 11) in PLoS ONE. Asking 79 undergraduate students, both male and female, to rate their jealousy if their partner talked to an ex-romantic partner in a range of situations, they found that meals elicited the strongest emotion. The results show higher jealousy for face-to-face interactions, such as having coffee, but highest jealousy when those interactions included food. The results were consistent between males and females.

The authors suggest the results support the idea that food plays a big role in the nature of social relationships. The idea is that people assume sharing a meal enhances cooperation, as it represents sharing resources, and is an activity that strengthens the family unit.

Why dogs love bones

Credit: FLICKR CREATIVE COMMONS, LIZ WEST

Dogs and other pack canines evolved their large jaws and teeth in response to hunting as a group, according to new findings announced this month at the First Joint Congress for Evolutionary Biology in Ottawa, Canada (July 6-10). Researchers looked at the diets and traits of more than 300 dog species to unravel the relationships between feeding habit and physical form. They determined that as plains habitats spread around 8 million years ago, ancient canines turned to living in packs, and were able to catch larger prey by working together. As a consequence, their jaw muscles strengthened and their teeth grew, eventually allowing them to be classified as "hypercarnivores"—animals that eat more than 70 percent meat.

The ancestors of modern wolves share this adaptation of strong jaw muscles for clamping down on large prey, and domestic dogs have not lost this instinct, explaining why they gnaw on bones, said study co-author Joao Munoz-Doran of the National University of Colombia. "They have the tools to do that," he told BBC News, "and they want to use their tools."

Squirrels shake to scare snakes

Ground squirrels thrash their upright tails around whether a predator snake is nearby or not, making the behavior seem random, but a new analysis shows that they are warning snakes to stay away, as well as responding to alarms from neighboring squirrels. In a study published this month (July 11) in Proceedings of the Royal Society B, researchers tagged Pacific rattlesnakes and videoed the burrow entrances of California ground squirrels, enabling them to observe which behaviors allowed squirrels to avoid a venomous bite. They found that squirrels who fearlessly faced down the snakes while shaking their tails avoided being bitten more often than those who saw the snake, but did not shake.

The authors think the shaking likely shows off the squirrel's readiness to dodge an attack, signaling to the snake that an attack will likely miss. In addition, when one squirrel began to shake its tail in response to a snake, others nearby followed suit, even if they could not see the snake itself. Squirrels seemingly randomly shaking their tails were in fact shaking in response to the perceived threat felt by other squirrels, rather than a real threat they observed themselves.

http://www.youtube.com/watch?v=r2k2IRtlmoM

Birds sniff out a date

In the first documented example of scent selection in birds, storm petrels demonstrate the ability to smell the difference between relatives and potential mates. Researchers used a well-studied colony off the coast of Spain, where the family links of all birds is known, to determine whether the birds preferred to go towards the smell of a relative, or the smell of a stranger. Their results, published July 15 in Animal Behaviour, show that almost all the birds tested preferentially walk towards the unfamiliar smell.

The colony, on the Isla de Benidorm, has been studied for 18 years, during which time a related pair have never been found nesting together. Scent selection is widespread among mammals, but birds were previously thought to only use sight and sound to distinguish kin from potential mates. The new findings may help explain how the birds, that remain in the colony for their entire lives, can avoid mating with the many other family members that live in the same colony.