World & Indian History

Giant Panda Cubs Surprisingly small during birth, appear to be "undercooked"

A Giant Panda, also known as a Panda bear and unique to China, was reclassified from "endangered" to "vulnerable" on the IUCN Red List, confirming decade-long efforts to conserve the panda. 

Giant Pandas are becoming extinct due to the destruction of their habitats by humans, as well as their inability to defend themselves against any threat. These bears, unlike other scared bears, are sluggish throughout their life cycle. 

Let us now discuss enormous panda babies. Panda infants are not born enormous; rather, they are born very tiny and are often referred to as "undercooked" due to their size. New research on infant panda skeletons has found that the developmental stage of panda cubs when they are born would be deemed premature in practically any other mammal. 

In brief, gigantic panda bears are born at a time of gestation equivalent to the beginning of the third trimester in humans. A newborn panda cub weighs between 90 and 130 g (3.2 to 4.6 ounces).

A cub is only 1/900th the size of its mother (weighs around 120 kilograms (220 pounds)), making it one of the smallest newborn mammals in comparison to its mother. This is the lowest birth weight ratio of any placental mammal, while other mammals have a ratio closer to 1:26. Pandas rely on their moms for the first few months of life and are fully weaned at 8 to 9 months.

The birth weight of a panda infant has always been a mystery to scientists. The bears are born pink, squeaking, blind, and exceedingly tiny. 

All bears (family Ursidae) have very small cubs, but gigantic pandas are especially noticeable. This is a rare occurrence in monotremes and marsupials, which give birth to positively lilliputian babies and then intensively milk them, generally in a maternal pouch, until they have done baking. 

However, pandas and other bears lack pouches. As a result, Duke University researchers Peishu Li and Kathleen Smith decided to look at the skeletons of giant panda cubs to find out why tiny babies are born in the case of a giant panda. 

Giant pandas are extremely rare on Earth, hence skeletons of panda newborns are nowhere to be found and practically impossible to find. However, in the 1980s, five cubs were born to giant pandas Ling-Ling and Hsing-Hsing at the Smithsonian's National Zoo, but unfortunately, they did not survive long after birth. But their skeletons had been preserved by the zoo authority, and Li and Smith were able to perform micro-CT scans on two of them. 

The scientists also took scans of some other mammals' newborns - grizzly bears (Ursus arctos), sloth bears (Melursus ursinus), polar bears (U. maritimus), a red panda (Ailurus fulgens), a coati (Nasua narica), an African wild dog (Lycaon pictus), an arctic fox (Vulpes lagopus) and two domestic dogs (Canis familiaris), one of which was fetal. 

They created 3D scans of all the skeletons to carefully examine the level of ossification, or bone growth; whether the teeth had begun to form or erupt; and the fusion of the skull plates. 

After carefully examining the skeletons, they came up with the hypothesis that panda bears' low birth weight is due to hibernation; the idea is that if the pregnancy overlaps with hibernation, the period of fasting could result in an earlier birth when the mother's internal reserves become depleted

However, because giant pandas do not hibernate like regular bears, how did they come up with such a weird hypothesis? scientists suggest that low birth weight may have acquired a trait of bears in general throughout evolution. 

When scientists inspected and analyzed all of the skeletons in this study, they discovered that the skeletons of newborn bears were exactly as developed as the skeletons of the other newborn animals. This implies that bear cubs are born at full term. Except with one instance. The cubs of the giant panda.

Their bones mirrored those of the puppy fetus, which was delivered several weeks early, at roughly 70% of its gestation period. A giant panda's gestation cycle ranges from 97 to 161 days, which seems like a long time given how small the pups are. 

Previous research has revealed that this is due to delayed implantation, in which the embryo floats around in the womb for a few months before connecting to the uterine wall; it will only begin to develop after this attachment. 

Based on food availability, this is frequent in bears. However, pandas have a substantially shorter gestation period after attachment than other bears. They develop in the same way as other animals, but they emerge before they're ready. 

Peishu Li said that, 
"They're basically undercooked." 
The reason for this? Well, we still don't know. What we do know is that the size of adult bears has increased in the last 20 million years; perhaps while the bears grew, the birth weight of their cubs did not."

"Given its close phylogenetic affinity with other ursine bears and adaptations to a herbivorous diet like the giant panda, the cave bear may be a promising candidate to further shed light upon the relationship between phylogeny, herbivory, and reproductive physiology among Ursidae," according to the authors of the paper. 

Panda Breeding Facts:

1. At the age of 5.5 to 6.5 years, giant pandas reach sexual maturity.
2. A female can mate with multiple guys that compete for her attention.
3. A male will seek out different females who are on heat. 
4. The mating season is in spring between March and May.
5. Males and females often socialize for no more than 2-4 days.
6. Gestation takes from 95 to 160 days.
7. Pandas normally give birth to a single young.
8. Twins appear to be more common in captivity when artificial insemination is employed.
9. The reproduction rate is approximately one cub every two years.

The research was published in the " Journal of Anatomy"

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