Category Archives: evolution

Red squirrels are people too. They adopt

Red squirrel taking an adopted baby from nest. (Photo/Ryan W. Taylor)

In another life, I must’ve been a dog. Whenever I’m out walking and see a squirrel, I have an almost uncontrollable urge to see how close I can get to it before the scrappy rodent scrabbles up a tree. Inevitably, a staring contest ensues, which the squirrel usually ends up winning.

My suppressed animal urges aside, I do notice something kind of educational about squirrels. They tend to be alone. When they’re not, they are usually chasing each other like crazed maniacs in a not too friendly manner without regard to life or other happenings.

That’s why it might come as a surprise that they practice a typically human behavior – they adopt. And they adopt outside their social group. A new study by researchers at the University of Alberta determined that red squirrels will take in abandoned or otherwise parent-less young and raise them as their own, a seemingly altruistic act. The behavior turns out not to be as charitable as it sounds – the squirrels do get a survival perk. But the discovery is nonetheless an unusual one in the animal kingdom, with its own squirrely flare to boot.

Jamieson Gorrell, a Ph.D. student in evolutionary biology at the University of Alberta and lead of the study, was observing a population of Yukon red squirrels and noticed a lone female had taken a baby from an abandoned nest to raise as her own. When Gorrell sifted through 20 years of red squirrel research from the area, he found four other instances of the same behavior. Not only that, but in each account, the baby adopted was a relative.

Gorrell found that despite their antisocial tendencies, red squirrels are still able to recognize, and decide to care for, relatives. Right now the predominant notion is that the chitter-chatter squirrels screech out to mark territory or ward off others contains vocal clues about relativity. So an encroaching squirrel could hear the calls of another adult, and recognize kinship. If that other mother disappears, the encroaching squirrel may recognize the kinship of the abandoned nest and take action.

In addition to the novelty factor of the behavior, the study authors also state that this finding proves a long-standing evolutionary theory true. It is a concept known as Hamilton’s Rule, which suggests that despite “the law of the jungle and survival of the fittest,” animals can be altruistic.

Though for red squirrels, it’s a tempered altruism. The red squirrel is still helping out a member of its bloodline, and will only help one baby out of a litter. Adopting more than one is “out of the question,” according to the study, as the strain of adding more than one baby to a single mother’s already full house would outweigh any benefits.

You can read more about the study in the online journal Nature Communications, or visit this link http://www.redsquirrel.ca/KRSP/Media.html to get more info, cute pics, and free copy of the study.

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Surfing crocodiles take to the high seas

A 4.8 m male estuarine crocodile ready for release with satellite transmitter. This crocodile traveled over 590 km by sea. (Courtesy/University of Queensland)

Next time you’re out sailing the high seas and think you’ve spotted a crocodile hanging ten, no need to get your eyes checked just yet. Turns out crocs do surf ocean currents, albeit sans boards and all the crazy wipeouts.

The behavior tracked by researchers out of Queensland, Australia, helps explain why the reptiles are so widespread, yet genetically similar.

Estuarine crocodiles which typically live in saltwater habitats like rivers and mangroves occupy a range covering about 10,000 km2 stretching from East India to Fiji and southern China to northern Australia, said the study. Geographic isolation tends to support the evolution of different species. But despite living in places separated by thousands of miles of open ocean, a crocodile living in Fiji is likely the same kind of croc living in Australia.

“The estuarine crocodile occurs as island populations throughout the Indian and Pacific Oceans, and because they are the only species of salt-water living crocodile to exist across this vast area, regular mixing between the island populations probably occurs,” said Hamish Campbell with the University of Queensland, and study lead in a press release.

But until now, scientists weren’t sure how. Stories have floated in over the years of ocean-bound crocodiles, even though the toothy predators are no Mark Spitz when it comes to swimming. Campbell and his colleagues from Queensland Parks and Wildlife Service and Australia Zoo set out to monitor the mobile capacity of crocs. They used acoustic and satellite tracking to follow the movements of 27 adult crocodiles over the course of a year. The crocodiles revealed an astonishing range of movement, regularly traveling 50 kilometers or more from their stomping grounds to the mouth of the river and out into the sea.

Croc’s, it seems, like to “go with the flow,” according to the researchers. Tides and currents dictate the timing and extent of a crocodile’s swim, with crocs typically beginning a swim within an hour of a changing tide, following the movement of the water, and returning to shore when water is no longer headed in the desired direction. Similar behavior applies to swims in the open ocean, where crocs ride the currents.

One croc, a roughly 15-foot- long male, traveled more than 400 kilometers in 20 days from the east coast of Cape York Peninsula through the Torres Straits to the west coast of Cape York, according to the study. At one point, the croc stopped on the shore of the Torres Straits and stayed there for four days waiting for more ideal currents.

Campbell explains that this type of behavior, “not only helps to explains how estuarine crocodiles move between oceanic islands, but also contributes to the theory that crocodilians have crossed major marine barriers during their evolutionary past.”

The full paper is available in the British Ecological Society’s Journal of Animal Ecology.


Monarch flycatchers: Catching the moment one bird species becomes two

Plumage variations of the monarch flycatcher. (Photo/Courtesy J. Albert Uy)

Plumage variations of the monarch flycatcher. (Photo/Courtesy J. Albert Uy)

How do you measure the instant one species becomes two? Well, in the Solomon Islands, biologist J. Albert Uy is trying to pick a fight with monarch flycatchers to find the answer. The fight’s tipping point has to do with a bunch of feathers, a change in plumage colors that is allowing scientists to capture a snapshot of evolution in action.

A territorial flycatcher (Monarcha castaneiventris castaneiventris) aggressively responding to a taxidermy mount during our mount presentation experiment. We used mount presentation and song playback experiments to test if divergent plumage color and song are used in species recognition between sister taxa (described in Uy et al. 2009). (Photo/Courtesy J. Albert Uy)

A territorial flycatcher (Monarcha castaneiventris castaneiventris) aggressively responding to a taxidermy mount during our mount presentation experiment. (Photo/Courtesy J. Albert Uy)

Flycatcher males are territorial and will launch an avian smackdown towards perceived rivals trespassing on their turf. But a flip of a single gene is turning the monarch flycatcher into a bird of a different color, and in the process changing the social dynamics of rival birds.

It seems that though they are technically still the same species, the black-feathered flycatcher didn’t get the memo about their chestnut-bellied kin, and vice versa. Uy tested this by invading flycatcher territory with dummy birds. What he’s found is that the two don’t see each other as rivals, and are therefore probably more interested in mating with their like-feathered counterparts.

At least in the case of the monarch flycatcher, this single gene and spot of color heralds the birth of an entire new species.

J. Albert Uy (Photo/ C. Low, courtesy J. Albert Uy)

J. Albert Uy (Photo/ C. Low, courtesy J. Albert Uy)

We often hear about species being lost, but rarely do we learn of one being created. Uy’s work provides a glimpse of the “fork in the evolutionary road” as it happens in real-time, and what that could mean for our understanding of bird life.

Uy’s work appears in the current edition of American Naturalist, and you can read more about monarch flycatchers in the 2005 New York Times article, “In Give and Take of Evolution, a Surprising Contribution from Islands.”


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