Sunday 18 February 2024

Polar bears, joking apes, & predicting dementia | Last Week in Science (18th Feb 2024)

Will they survive?

With the global average temperature crossing the 1.5 degrees mark, the concern for animals in the Arctic and Antarctic has increased. Polar bears are one such organism that have been predicted to not survive the longer ice free days of the Arctic based on the studies done so far. Although, what these studies did not include were the differences in behavior, age, activity and thus energy expenditure of different bears. Researchers in Canada and USA studied polar bears in the Western Hudson bay to observe the differences between individuals.

Polar bears hunt and survive on seals exclusively. During the ice free period of summers they spend time on land - which has now increased to around 130 days and is expected to increase in the coming years based on the changes in the climate due to global warming. The scientists hypothesized that adult polar bears which have larger mass and more fat than females and younger bears would be able to hibernate and conserve energy when on land. While the younger bears would spend more time looking for and eating food sources that are available on the land in the absence of seals during that time of the year - with females foraging more as compared to younger adult males because of their smaller size - less fat and so more need for energy.

The scientists made these observations by making the bears wear GPS equipped cameras. They found that the age and size did not affect the hibernating or foraging behaviour of polar bears. Their energy expenditure based on their activity was dependent on the behaviour that had a high variation. Even though swimming is a high energy consuming activity, yet they found some of the bears, both males and females swimming. Polar bears were seen to lose body mass as the food available on land could not meet their energy needs. During hibernation, bears depend on the fat reserves in their body. But the scientists observed loss in lean muscle body mass instead of the depletion of fat reserves. It is another proof that the bears will not be to survive for long on the land for long because of eventual starvation. Although, it may be too complex to predict the overall behavior and adaptations of bears because of the high variations observed, the study still reiterated what we know.

Reference: Polar bear energetic and behavioral strategies on land with implications for surviving the ice-free period

Apes have a sense of humour

"Humor is mankind's greatest blessing." - Mark Twain

Humorous behaviour like joking and teasing (without harming the other individual) seems to increase bonding amongst individuals. Even infants as young as 8 months of age, who haven't even begun speaking show teasing behaviour like offering their toys and then pulling it back or taking something the moment you want to use it. 

Guess what, such behaviour is not just seen in humans but great apes like bonobos, gorillas, orangutans, and chimpanzees also show such teasing amongst themselves. Scientists in the University of California recorded these four different great ape species and got some 75 hours of video footage. They looked for signs of playful teasing, which is neither aggression nor play but one sided and involved one individual being targeted. This mostly involved poking, hitting, or pulling hair in the case of orangutans. This kind of behavior is also observed in human siblings and friends who are of the same age, but in the great apes the younger ones engaged with the adults to show such playful teasing.

But why study teasing in apes? Humour is a behaviour that utilises a lot of mental ability - judging of the situation, prediction of others' response and seems to be a way for bonding amongst individuals. Presence of this behaviour in apes who share a common ancestor with humans indicate that humourous behaviour evolved some 13 million years ago. So similar studies can help us in better understanding evolution of other behaviours and emotions. 

Reference: Spontaneous playful teasing in four great ape species 

Blood tests for early diagnosis of dementia

Dementia is a condition that is associated with memory loss and gradual decline of brain functioning. It is a condition seen in many neurodegenerative disease. It is usually too late by the time the disease is diagnosed because of the absence of diagnostic tests. Brain scans are done only after a substantial decline in mental functioning is seen, which shows the damage inside the brain. Scientists have been looking for blood tests that can help in the diagnosis of diseases that cause dementia before the symptoms appear.

Scientists at Fudan University, China have now found a blood test that can diagnose dementia as early as 15 years before the symptoms start to appear. They looked at some 52,000 human samples (taken from UK Biobank) and identified 1400 individuals that had developed dementia when followed up after 14 years. Using this data, they could find four different proteins in the blood that were found to have increased in individuals that developed dementia 14 years before they developed dementia.

We can hope for a blood test to be available once this study is tested and repeated again for consistency and robustness.

Reference: Plasma proteomic profiles predict future dementia in healthy adults

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