SciSun: Ya talkin’ to meese?   Leave a comment

A mouse, is a mouse, is a mouse. (Actually there are over 1000 different types of ‘Myomorpha’, or ‘mouse like rodents’). But the popular image of a mouse is one that hides under your house and comes into the kitchen at night to eat cheese. Why someone would leave cheese out at night we don’t know. But while this ‘standard’ House mouse (Mus musculus) might be the most familiar rodent among all mice, the real story of ‘city mouse or country mouse’ is found among Peromyscus leucopus, the White Footed Mouse, a native species that has lived among humans for thousands of years. And today scientists are finding there are significant differences within this one species not due to centuries of evolution nor changing climate nor even geologic isolation of small populations – but from living in the city.

New York City is the most densely populated city in the United States, with over 8,500,000 people within 305 square miles. (As a comparison the Los Angeles metropolitan area is approximately 500 square miles with a population under 4 million). Also in New York you will find countless numbers of urban wildlife including coyotes; raccoons; possums; bats; millions of birds; and millions more rats and mice. Just as many New York humans are most comfortable staying within one borough – an area within the City large enough to be cities themselves – New York White Footed mice are content to live within one neighborhood. Or city park. Or vacant lot. And each of these areas – tiny mice boroughs in themselves – is showing that not only do mice (and humans) take on unique characteristics of their chosen neighborhood, but among White Footed mice is resulting in genetic differences that distinguish individual mouse populations from their cousins, still of the same species, but living in different areas of the City. Just like a resident of Brooklyn would never, ever be confused with someone from the Bronx.

“Yea, so some guy sez ta' me he sez  'How do I get to Carnigie Hall?  I tell'm practice, lots a practice'. What's you lookin' at?”

“Yea, so some guy sez ta’ me he sez ‘How do I get to Carnigie Hall? I tell’m practice, lots a practice’. What’s you lookin’ at?”

Historically White Footed mice have not lived in close contact with humans, but on the edges of human development, favoring the border and edge areas of forests, fields, and meadows. These White Footed meeses (the plural of ‘mice’. We think.) prefer to remain within a small territory, seldom venturing more than a few hundred feet and when among humans hesitant to venture too far into ‘civilization’ but remaining in vacant lots, parks, and among roadside greenspaces. Scientists have long observed differences in behavior between these city-edge mice and their country-side counterparts; however only recently has the extent of these differences been uncovered. Looking at the DNA of almost 200 mice from 23 different city locations, it’s been found that the White Footed population has undergone two distinct evolutionary landmarks that forever changed, at the most basic level, the species: About 12,000 years ago at the end of the most recent ice age, receding glaciers shaped the geography of much of what is now the Eastern US, creating unique evolutionary distinctions among those species that survived the climatic changes. As the ice ages were an Earth-wide event, similar genetic changes are found in other species. But the second genetic change occurred only 400 years ago, just a moment in evolutionary time, when the area that is now New York City was shaped not by climate but by the arrival of Europeans and the resulting changes from meadows and forested land into agricultural fields, housing, roads and other development. The city mice have developed stronger, more resistant immune systems; differences in intestinal bacteria which helps the mice digest (and survive) less-than-wholesome foods; tend to be more acrobatic than the forest-and-field mice, bounding over vacant lot trash and sprinting among weedy tangles; and within each borough have become so genetically distinct from mice of other boroughs it’s possible to tell exactly in what area each mouse lives. All without checking their transit card.

These mice-sized discoveries are generating a mighty amount of work, as scientists around the world are investigating whether other urban wildlife species have developed not only behavioral changes, but evolved genetically. In this new field of urban evolutionary genomics, researchers are looking into the lives (and DNA) of urban coyotes; pigeons; rats; and other species; it’s already been noted that a certain type of Australian urban spider has evolved a larger body and greater reproductive abilities; and in the Netherlands urban birds sing louder and at a higher pitch to be heard among city sounds. Just as humans have shaped the cites we live in, it seems we’ve also shaped the wildlife that share those cities. And the louder and busier and more complex our lives become, urban wildlife are right there among us, evolving to fit into the city as they remain wild and untamed. Which, according to some opinions, is the perfect and only way to survive in the big city.


Michonne Says: Marmots try to stay away from human places but if any marmots did want to live there (and I don’t know why they would), they would probably change and be different, too. There’s that groundhoggy that the men look at for a shadow or no shadow and I think he lives near humans and they never leave him aloneThat’s enough to change anybody.

Posted April 24, 2016 by ECOVIA eco-adventure® in SciSun

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