Gulls love garbage; pikas love cold
Garbage allows gulls to thrive in the oilfields of northern Alaska, and furry little pikas might be changing their body shapes in response to changes in climate, according to two graduate students who recently gave public defenses of their theses at the University of Alaska Fairbanks.
Emily Weiser spent a few summers on Alaska’s North Slope, studying glaucous gulls, creamy white and gray birds most people refer to as “seagulls.” The birds spend their summers off the north coast of Alaska and inland up to about 100 miles.
Weiser studied gulls at Barrow, Alaska’s northernmost city; at Cape Simpson, where no people live; at Alpine oil field, in the North Slope’s Colville River Delta; and at Deadhorse, a town just south of Prudhoe Bay. She wanted to see if the presence of available garbage enhanced the population of glaucous gulls, which eat just about everything, including the eggs and chicks of other birds.
“Glaucous gulls are the most abundant human-subsidized predator (in the oilfield area),” Weiser said.
She teased apart pellets the gulls had coughed up to look for the presence of plastic. The birds around Deadhorse — where there is an open landfill, unlike Barrow and the Alpine oil field, where garbage is incinerated — had a huge percentage of garbage in their diets. Using those results and some statistical analysis, she concluded that birds with access to open garbage dumps seemed to be doing better than others. For instance, garbage-consuming groups of gulls experienced higher fledgling success.
Weiser mentioned a study in which researchers found that only about four out of 10 gull chicks migrate back to the same area in which they were born. Without human-related sources of food, the wayward birds might be hitting the eggs and young of other birds, such as black brant, northern pintails, arctic terns, and shorebirds.
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Pikas are cute, fist-size mammals with round ears that live in lonely rock piles in Alaska’s high country. Despite their hamster-like appearance, they are more closely related to rabbits, and they survive the winter beneath the snow, eating vegetation they stacked in piles during summer.
Hayley Lanier studied collared pikas, which live on talus slopes in Alaska and northwest Canada, for her doctorate at UAF. One of her goals was to see if pikas might have adapted to the warmer temperatures of recent decades. Pikas are intolerant of high summer heat, and a species of pika in the lower 48 states has disappeared from spots down there, possibly because their high-country habitat is becoming too warm. Lanier measured skulls of pikas that people had collected for the UA Museum of the North during the last 60 years.
She and her advisor Link Olson noticed that a man named Robert Spooner had collected a good number of the pika specimens that she had used in her study. After wondering for several years about the person who had so carefully prepared the delicate skins, Olson found Spooner’s name in the Fairbanks phone book and invited him to attend Lanier’s thesis defense. He accepted.
A UAF graduate student in the early 1960s, Spooner used a .410-gauge shotgun loaded with No. 9 shot to retrieve pikas from several locations in Alaska before deciding “research wasn’t my bag” and becoming a teacher in Fairbanks.
Lanier compared the body size of pikas Spooner had collected off the Denali Highway to pikas she found in the same area 45 years later. She found the more modern pikas had larger skulls and a shorter body length.
“They got more spherical,” she said.
On hot summer days, pikas hunker down beneath rocks where the air is cool. Extended bouts of hotter days might prevent larger pikas from gathering enough food to survive winter, Lanier said. But since pikas don’t hibernate, larger, warmer bodies would seem to be an advantage during winter. This evolutionary tug-of-war between large and small body sizes has probably kept pikas’ body size constant, but it may have shifted during the last 40 years or so. Lanier thinks the apparent increase in pika body size might be due to more midwinter thaws of snow.
“We tend to assume that warm-blooded animals will get smaller to conserve energy as average temperature increases,” Olson said. “But, in this case, pikas may be having to adapt to colder temperatures beneath a thinner snow cover.”
