Are tortoises starving to death in Joshua Tree? - via Herp Digest

December 17, 2013, Conservation This Week

The corpses of apparently starved and dehydrated tortoises are littering part of Joshua Tree National Park, and the culprit may be climate change.

In 1978, researcher John Barrow began surveying Agassiz’s desert tortoises in a one-square-mile patch of the park in the Sonoran Desert, California. During that year, Barrow marked any tortoises he found by notching their shells with a metal file. Other researchers continued the work in the 1990s and early 2000s, marking the animals with epoxy tags or yellow or green paint.

The authors of the current study returned to the site in 2012 and conducted 14 surveys of the plot. They searched for tortoises and investigated burrows with flashlights and sticks. The team also collected coyote scat to find out if these predators had eaten tortoises.

The researchers found 14 living and 64 dead tortoises, they report in Biological Conservation. About 30 percent of the deaths probably occurred since 2008. “The postures and positions of a majority of dead tortoises found in 2012 were consistent with death by dehydration and starvation,” the team writes.

The estimated number of tortoises also dropped from about 200 to less than 50 between 1996 and 2012. Many of the carcasses had been picked over by other animals; some tortoises were missing their heads or limbs, and four coyote scat samples contained tortoise remains.

The authors speculate that longer, more frequent droughts may have hastened the tortoises’ deaths. The dry weather might also have caused small mammals, such as rabbits, to reproduce less. Faced with a food shortage, predators that normally eat rabbits might have then attacked tortoises instead. — Roberta Kwok | 17 December 2013

Source: Lovich, J.E. et al. 2013. Climatic variation and tortoise survival: Has a desert species met its match? Biological Conservation doi: 10.1016/j.biocon.2013.09.027.

Why Some Animals Are Fatter Than Others

Humans are often obsessed with their weight, but nature seems to know exactly how fat each animal on the planet should be. The perfect weight depends on how each species solves the problem of avoiding both starving to death and being killed by predators, new research suggests.

The study, published in The American Naturalist, explains how these causes of death often exert opposite pressures on animals. Storing a lot of fat, for example, helps animals survive periods without food but also slows their running speeds and so makes getting caught by a predator more likely.

Animals can be stronger to compensate, but the energetic costs of extra muscle mean that the animal would starve more quickly during a food shortage.

Continued:  http://www.livescience.com/18054-animals-fatter-survival.html

Robins in Scotland battle for survival

EDINBURGH, Scotland, Dec. 23 (UPI) -- Robins, icons of the Christmas season, don't practice peace and goodwill with each other and often turn murderous toward their own kind, U.K. researchers say.


Experts with Scottish Natural Heritage said the festive songbirds think nothing of bumping off their rivals to ensure they get their beaks on enough food to survive, The Scotsman reported Thursday.

About one in 10 robins is killed by another bird of the same species as both males and females enter into vicious battles over territory and food, a wildlife expert said.

"Traditional images of peaceful robins adorn our Christmas cards at this time of year, but this harmless-looking bird is actually a territorial terror," said Tom Cunningham, reserve manager at Tentsmuir National Nature Reserve.


"As well as defending territory during mating, they will often fight other robins, sometimes to the death, over scarce food resources in winter," he said.

Heavy snows sweeping across Scotland have buried their usual food supplies, he said.

"A lot of birds and animals are starving this winter," he said. "It's not surprising that they're fighting each other for what they can get -- it's survival of the fittest at the moment. They really are territorial creatures."


http://www.upi.com/Science_News/2010/12/23/Robins-in-Scotland-battle-for-survival/UPI-67011293138907/

Barn owls starving to death in the freeze

Snow fun for barn owls as numbers reported dying this winter grows

December 2010. The RSPB is receiving a growing number of calls from members of the public who have discovered dead barn owls recently. Although owls have been found dead in a range of locations, there has been a significant number found in barns and out-buildings.

Starving
Experts at the RSPB believe it is because the cold weather is making food almost impossible to find and the birds are dying of starvation within their roosting locations.

The wildlife charity is worried that the current big freeze can only make this situation worse and is appealing for vigilance where the birds are known to be roosting in the coming weeks.

Barn owls feed on small mammals like voles and mice, and with the ground frozen and covered in snow, this food is almost impossible to find.

Younger owls suffer most
The problem is likely to be most serious for barn owls born this year, that are less experienced at dealing with difficult conditions. It is thought that these first year birds will account for a high percentage of the mortality.

All owl death reports received so far are about barn owls, and the RSPB believes this is likely to be because they commonly live close to man, usually in out-houses, barns and farm buildings, so they are easier to notice.

Mark Thomas, RSPB Investigations Officer says: "We have been receiving a growing number of calls from people who have discovered dead barn owls in recent days and we believe it's because they are starving in the cold weather as the icy, snowy conditions make their main food sources like voles and mice much harder to find.

What to do?
"Although practically there is little that can be done to supplement the diets of barn owls, farmers and members of the public are encouraged to remain vigilant and report any sick or injured looking owls to a wildlife rescue centre immediately. It's very distressing for both the birds and the people who discover them, as they are beautiful and charismatic species of the British countryside.

"Prompt action could save the life of a starving bird and once they've been fed up they should soon be fit for release back in the original location."

Barn owls are most commonly seen at dusk, in open country, along field edges, riverbanks and roadside verges. They nest and roost in buildings found near these habitats, such as farm outbuildings and barns.

Despite the UK Barn owl population doing well in recent years, a high mortality event such as this could have serious conservation implications.
http://www.wildlifeextra.com/go/news/barn-owls010.html