Bright lights, beady eyes? Looks like city lights might be causing an evolutionary adaptation that sees some birds develop smaller eyes to deal with the constant light in urban environments. A new study published in Global Change Biology found that two common songbirds, northern cardinals and Carolina wrens, that lived year-round in the urban core of San Antonio, Texas, had eyes that were five per cent smaller than their country cousins’. 

Interestingly, migratory birds that lived in the city only part of the year did not show any difference in eye size, suggesting that while resident birds may be adapting to life in the city, migratory birds are not, which could put them at a disadvantage during the part of the year when they’re in the city. (It’s theorized that birds with bigger eyes can be somewhat blinded by the glare of city lights or less likely to sleep well.)

Pass the porpoise

If you thought a cat with a mouse was nasty, wait till you hear about the orca and the porpoise. Just like cats, Southern Resident killer whales are highly picky eaters, basically accepting nothing but Chinook salmon for dinner. In other words, these predators don’t often chow down on porpoise, so have no reason to attack them. But if a porpoise crosses their paths, it’s playtime.

Over the last six decades, scientists have recorded 78 instances of resident orcas harassing porpoises in the Salish Sea between B.C. and Washington State. They might push the porpoise along with their nose, hold it in their mouth, bounce it up and down, allow it to escape briefly before grabbing it again, and sometimes even play “pass the porpoise” with others in the pod. The one thing they don’t do is actually eat the porpoise.

Researchers, who published their findings in Marine Mammal Science, have three theories. Could it be a cruel form of play? Is it hunting practise? In a few cases, are the orcas attempting to care for the porpoises, treating the smaller, weaker porpoises as though they were the orca’s own young? Whatever the truth is, meeting up with the orcas is bad news for a porpoise.

Waning walrus

The last remaining stocks of Atlantic walrus are more at risk than ever, say researchers from Lund University, Sweden. The combination of Arctic warming and historic human exploitation has made them more vulnerable to pressures such as ice loss, Arctic shipping, resource extraction and mass tourism.

The researchers examined how walrus coped with past cycles of climate change by sequencing and analyzing ancient genetic information contained in teeth and bones frozen in Arctic archaeological sites. “We found that Arctic warming has led to a surprisingly high genetic separation of local walrus stocks,” says Peter Jordan, professor of archaeology at Lund University. Very specific habitat requirements meant the last Ice Age and the subsequent warming period that followed caused spreading, isolation and extinction in many walrus stocks as they migrated with the ice edge. 

And in the last thousand years, human hunting — from the expansion of Norse settlers to the modern industrial scale culling of walrus — has led to numerous local extinction events.

As a result, genetic diversity has reduced to a fraction of what previously existed, and species is therefore less prepared for the current period of climate change that’s causing Arctic sea ice to retreat; walrus will likely disperse further into smaller, more isolated pockets, further endangering their survival. 

A road to nowhere