(Press-News.org) University of Alberta researchers Péter Molnár, Andrew Derocher and Mark Lewis studied the reproductive ecology of polar bears in Hudson Bay and have linked declining litter sizes with loss of sea ice.
The researchers say projected reductions in the number of newborn cubs is a significant threat to the western Hudson Bay polar-bear population, and if climate change continues unabated the viability of the species across much of the Arctic will be in question.
Using data collected since the 1990s researchers looked at the changing length of time Hudson Bay is frozen over (the polar bear's hunting season) and the amount of energy pregnant females can store up before hibernation and birthing.
An early spring-ice breakup reduces the hunting season making it difficult for pregnant females to even support themselves, let alone give birth to and raise cubs. Pregnant polar bears take to a maternity den for up to eight months and during this time no food is available.
In the early 1990s, researchers estimate, 28 per cent of energy-deprived pregnant polar bears in the Hudson Bay region failed to have even a single cub. Researchers say energy deprived pregnant females will either not enter a maternity den or they will naturally abort the birth.
Using mathematical modeling to estimate the energetic impacts of a shortened hunting season, the research team calculated the following scenarios:
If spring break up in Hudson Bay comes one month earlier than in the 1990s, 40 to 73 per cent of pregnant female polar bears will not reproduce.
If the ice breaks up two months earlier than in the 1990s, 55 to a full 100 per cent of all pregnant female polar bears in western Hudson Bay will not have a cub.
The polar-bear population of western Hudson Bay is currently estimated to be around 900 which is down from 1,200 bears in the past decade.
The number of polar bears across the Arctic is estimated to be between 20,000 and 25,000.
The research team says because the polar bears of Hudson Bay are the most southerly population they are the first to be affected by the global-warming trend. However, they say that if temperatures across the Arctic continue to rise, much of the global population of polar bears will be at risk.
INFORMATION:The research will be published in Nature Communications, Feb. 8
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Bacteria often attack with toxins designed to hijack or even kill host cells. To avoid self-destruction, bacteria have ways of protecting themselves from their own toxins.
Now, researchers at Washington University School of Medicine in St. Louis have described one of these protective mechanisms, potentially paving the way for new classes of antibiotics that cause the bacteria's toxins to turn on themselves.
Scientists determined the structures of a toxin and its antitoxin in Streptococcus pyogenes, common bacteria that cause infections ranging from strep throat to life-threatening ...
Toronto – Faster approval times for generic drugs will get them into consumers' hands quicker, but may not make the price any better, a pricing and marketing researcher has found.
A mathematical model created by Andrew Ching shows that fewer firms enter the marketplace because the chances of getting there first and commanding the best profits are dramatically smaller when drug approval times are shorter. Ching is an associate professor of marketing at the University of Toronto's Rotman School of Management.
Using the drug clonidine, Prof. Ching's model showed the number ...
For Immediate Release – February 8, 2011 - (Toronto) – A new study from the Centre for Addiction and Mental Health (CAMH) has found evidence suggesting that a variation of a specific gene may play a role in late-onset Alzheimer's, the disease which accounts for over 90% of Alzheimer's cases. This innovative study has combined genetics and brain imaging to determine who may be at risk for developing late-onset Alzheimer's disease long before symptoms appear.
The gene, which is called brain-derived neurotrophic factor (BDNF), is crucial to maintaining healthy function of ...
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"We collected a random sample of regular large shell eggs ...
University of British Columbia researchers have uncovered the unique survival mechanisms of a marine organism that may be tiny, but in some ways has surpassed sharks in its predatory efficiency.
Published today in the journal Nature Communications, the research team's portrait of the microscopic dinoflagellate Oxyrrhis marina reveals a predator so efficient that it has even acquired a gene from its prey.
NB: A microscopic photo of Oxyrrhis marina is available at http://www.publicaffairs.ubc.ca/?p=17636.
"It's an interesting case of Lateral Gene Transfer, or the movement ...
Much of the devastation of stroke and head trauma is due to damage caused the overproduction of a substance in the brain called glutamate. Preventing this damage has been impossible, until now, as many drugs don't cross the so-called blood-brain barrier, and those that do often don't work as intended. But a method originally devised at the Weizmann Institute of Science may, in the future, offer a way to avert such glutamate-induced harm.
Prof. Vivian I. Teichberg of the Institute's Neurobiology Department first demonstrated a possible way around these problems in 2003. ...
Post-traumatic stress disorder can affect soldiers after combat or ordinary people who have undergone harrowing experiences. Of course, feelings of anxiety are normal and even desirable – they are part of what helps us survive in a world of real threats. But no less crucial is the return to normal – the slowing of the heartbeat and relaxation of tension – after the threat has passed. People who have a hard time "turning off" their stress response are candidates for post-traumatic stress syndrome, as well as anorexia, anxiety disorders and depression.
How does the body ...
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Babies whose mothers have HIV, but who are not HIV-infected themselves, are born with lower levels of specific proteins in their blood called antibodies, which fight infection, compared with babies not exposed to HIV, a new study has found. The finding, published today in the Journal of the American Medical Association, might explain in part why uninfected babies born to women with HIV have a higher risk of illness and death early in life.
Major programmes using antiretroviral drugs have successfully reduced the rate of mother-to-child transmission of HIV from 20-30 per ...
