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Choose shrew-like creatures as more sociable ancestors!

By Dave Armstrong - 23 Nov 2015 9:22:1 GMT
Choose shrew-like creatures as more sociable ancestors!

We rarely think about him in his burrow. Common assumptions about his social life simply recount that babies cling vice-like to their mother and each other in a long chain. What does the Eurasian shrew, Crocidura leucodon, make of us? Bicoloured Shrew image; Credit: © Shutterstock

The shrew has a unique character that we have unlimited opinions on. Some think they are mouse-like and aggressive loners, while others see them as pointy-nosed insectivores that live short and busy lives. The truth is both exist but there is much more to it. We have only 16 shrew species that have been well-studied, most conforming to the expected solitary pattern. Experts are now pointing out that a total of 445 species related to shrews are currently running around with more than half of them living in some kind of community. The fact that most are quite sociable greatly alters how we assume evolution has dealt with them since our earliest origins. From these arguments, we can delve further into the ancestors of all mammals, even including ourselves, and realise how social systems could have operated from the earliest example - those that resembled modern shrews!

The composition of a group, from the pair-bond up to the great troops of animals sometimes found interacting in true societies, affects all interactions and especially mating systems. We know mammals are extremely diverse. The key issue in an intriguing scientific paper is that previous ideas are disproved by evidence that will not support such traditional assumptions. Did solitary shrews evolve into more social ancestors such as the small taxons of the cats, the cattle or the monkeys? These latter 3 groups (carnivores, artiodactyls and primates) are in fact the only ones that have been investigated for their social lives. The small mammals have never been explored as early proponents of lives to be lived together by many more mammals..

If we look at the mole/shrew/hedgehog/solenodon group, we have the 3rd largest mammal group after bats and rodents. Around 380 shrews and 40 others give us a very wide picture of how living small mammals have adapted to their extant niches. 399 of these animals were used in a single database comparison of their social organisations, and 46 more were added, all belonging to this inelegantly-named Eulipotyphla! The placental mammals first appeared as shrew-like animals in shrew-like niches, so to compare them is not a mistake.

Several types of social group were found by the dogged authors in their paper entitled Social organization in Eulipotyphla: evidence for social shrews. Social groups occur in many species, with seasonal conditions seeming to determine how they gathered together. The Biology Letters of the Royal Society published the paper by M.Valomy, LD. Hayes and C Schradin of the Universities of the Witwatersrand,RSA, the UPMC, Paris and the University of Strasbourg, France and the University of Tennessee at Chatanooga, US today. The shrew proof is that they are much more sociable than formerly believed. Power is provided for the argument that the ancestor of all of us could have been a member of a pair, not the most obvious solitary little animal that is often suggested. Reliable evidence once again disproves the accepted norm.

From the conservation point of view, tree shrews are much more threatened than the ubiquitous shrew spp. Crocodilus species are so numerous that they outnumber any other mammalian genus. Here are SE Asian tree shrews rapidly disappearing as those beautifully rich, diverse forests go down under the saw.