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A Small mammal of the Quaternary: A Review of Brace et al

During the late-Quaternary it has been commonly noted that many large animals (the megafauna) became extinct. The smaller animals are often ignored, but this is probably because many of them survived into the present day (Brace et al., 2012). One such species is the collared lemming, which still exists in arctic regions today. This is a cold-adapted animal, which thrives during glacial conditions. Though this species remains extant, and it is often assumed that small animals were not largely affected by late-Quaternary extinctions, this lemming possesses a more complex story.

Collared Lemming: Dicrostonyx torquatus

The Story

Data collected from three sites suggests that the collared lemming underwent a series of localised extinction events, followed by recolonisation of those areas after initial disappearance. Several of these extinctions occur during climatically warm episodes (Brace et al., 2012). As a cold adapted species, it makes sense that regional extirpation would occur at this time. Whilst in contrast one of these events occurs during a period of cooler temperatures (Last Glacial Maximum). This coincides with the only known reduction in Mammuthus primigenius presence across the North of Europe during this time frame (Brace et al., 2012). So, it seems that this period of climate change has had a significant enough affect as to limit the distributions of both some of the large and small animals of the late-Quaternary.

European sampling sites of the collared lemming. Pot Cave, 
Caverne Marie-Jeanne and Trou Al'Wesse.

(Brace et al., 2012 p. 20533)

Why so many extinctions?

• It may have been climate, but the lemming was still occurring at Pot Cave, which was further North (see map).
• A link between climate and ecology: with a change in temperature and rainfall, there will be a corresponding change in vegetation type. This could have caused the repeated regional demise of the collared lemming. During warmer conditions vegetation was replaced by southern communities (Prost et al., 2010). Lemmings did not survive well in these environments, and experienced significant population contractions during these intervals (Brace et al., 2012). This could explain the repeated extinction events.

• It could be a response to loss in genetic diversity. Without this diversity, a population can fail to reproduce (Brace et al., 2012). Lack of genetic variation can ultimately contribute to population collapse (Lacy, 1997), which is a possible explanation.

Lemmings have so far survived the Quaternary, and continue to live in northern regions today. Contrary to popular belief, they do not walk off cliffs (just for the record).

If the article by Brace et al (2012) is too dense, I suggest taking a look at this summary article in the Daily Mail:

HERE

 

Thanks for Reading!