From the BSG (Bear Specialist Group):
I know you’ve been anxiously awaiting the answers to the New Year’s puzzlers. There were 3 True/False questions, stemming from papers published in 2017. Please note, that these answers are based solely on the cited papers, and may or may not be correct, If you have rebuttal comments, please share:
- The distinctive black and white coloration of the giant panda is an adaptation stemming from its diet of bamboo.
- Hybridization among bear species has been common in the evolutionary history of bears.
- The earliest, most primitive true bears hibernated; this trait was later lost in tropical bears.
- Source paper: https://academic.oup.com/beheco/article-abstract/28/3/657/3058530
This paper tested possible explanations for the distinctive color pattern of giant pandas. The authors concluded that the facial markings were used in communication, whereas the body markings were for camouflage in an environment that is sometimes dark (shaded forest with thick bamboo understory) and sometimes white (winter snow). Pandas are unique among temperate bears in being active during the winter when the ground is snow-covered (other bears are hibernating). The reason they are active is because their food is available even when it is cold and snowy. The reason for that is because their food is bamboo, not fruits. Hence, ultimately, they have their black and white pelage because they eat bamboo!
- Source paper: https://www.nature.com/articles/srep46487
Polar bear-brown bear hybrids have been in the news, and attributed to warming climates (brown bears moving north). However, a few papers have recently found that genetically, these 2 species show intermixing through their evolutionary history. Rarely, a few other hybrid bears have been found (e,g, Asiatic black bear-sun bears). This paper looks at the genetics of all species of bears and finds evidence of widespread inter-species mixing. This surprising finding apparently explains the often conflicting results of a number of studies about the phylogeny of bears. Similar evidence for inter-species breeding has been reported for other taxa as well. Notably, a new species of finch on the Galapagos Islands was reported to derive from the rare mating of 2 other species, just 36 years ago (https://www.princeton.edu/news/2017/11/27/study-darwins-finches-reveals-new-species-can-develop-little-two-generations).
- Source paper: https://www.nature.com/articles/s41598-017-17657-8
This paper discussed the skeletal remains of a small extinct bear (2 individuals) from the mid-Pliocene (3.5 million years ago), found in the High Arctic of Canada (where today there are only polar bears). The teeth of this bear indicated it was herbivorous and, because it had cavities, suggests it ate fruits (fruit-producing plants were found in this region at the time; this region was warmer than it is today). The only way for a frugivorous bear to survive winter in a place like this would be to hibernate. Since this “true bear” is one of the oldest ever found, the findings suggest that the most primitive bears were hibernators, which means that tropical bears, which evolved later, lost this ability. Note that this includes the Andean bear, whose ancestors of short-faced bears in North America would have hibernated.