Two interesting new uses for poop

Scientists have discovered two, er, interesting things animals do with poop – in both cases, not their own.

Honeybees use it to defend their colonies, while giant pandas roll in it to increase their cold tolerance. Both are effective strategies it seems, but one is a bit messier than the other.

An international team of researchers led by Wellesley College in the US has found that Asian honeybees (Apis cerana) collect animal faeces and carefully arrange it around their nest entrances to deter attacks by giant hornets.

In a paper in the journal PLOS ONE, Heather Mattila and colleagues say it is the first documented case of honeybees collecting non-plant matter, and the first clear example of tool use.

Giant hornets such as Vespa soror are voracious predators and launch group attacks on honeybee colonies.

In observational studies of three apiaries in Vietnam, the researchers found that A. cerana collected small balls of animal dung, which they applied in spots around nest entrances in response to visits by V. soror, but not in response to visits from a smaller hornet species (Vespa velutina) that does not attack in the same way.

They also found that colonies exposed to secretions from the glands that giant hornets use to mark for nests for attack had more faecal spots around their nest entrance after six hours than colonies exposed to a control.

Hornets were less likely to land on nest entrances with large numbers of faecal spots and spent much less time chewing at the entrance if they did land. The researchers suggest the faeces may contain compounds that either deter hornets or mask the chemical markers they use to target colonies for a mass attack.

European honeybees don’t use the same strategy, they note, and suffer the consequences.

And the pandas? As the Chinese researchers note in their paper in the journal PNAS, “Attraction to faeces in wild mammalian species is extremely rare.”

Nevertheless, they report 38 incidents in 2016/17 in which Qinling giant pandas were “observed to engage with horse manure”. Specifically, they sniffed it, rubbed it against their cheek, rolled in it, then smeared it over themselves. It happened most often when the manure was fresh and the air temperature between minus five and 15 degrees Celsius.

201210 panda poop
Panda with poop. Credit: Fuwen Wei

Hypothesising that the presence of chemical compounds beta-caryophyllene and caryophyllene oxide in fresh manure may drive the behaviour, the research team, led by the Chinese Academy of Sciences, found that in winter pandas at the Beijing Zoo preferentially sniffed, rubbed and smeared hay treated with those compounds.

They then found that mice treated with the compounds exhibited increased cold tolerance, and that beta-caryophyllene and caryophyllene oxide interact with pandas’ thermosensitive receptor pathway called TPRM8 and inhibit cold activation of the pathway.

Thus manure rolling may help pandas acclimatise to cold temperatures. Social distancing recommended.

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