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Why Male Ground Squirrels Disperse

My eco project.

Sam Keamy-Minor

on 22 April 2010

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Transcript of Why Male Ground Squirrels Disperse

Why Male Ground Squirrels Disperse By Sam Keamy-Minor Why do male ground squirrels disperse? Physiological Mechanisms Effect of Ontogenetic Processes Effects on Reproduction. Evolutionary Orgins Split question into 4 pieces. •First hypothesis: Levels of androgens elevate in males, causing squirrels to start dispersing Tested by removing gonads of both male and female squirrels. Observed dispersion rates of castrated males and females. Found no change. •New hypothesis: Exposure to hormones during development causes dispersion Inject recently born female ground squirrels
with androgen, and observed dispersion rates. The injected femails dispersed at
the same rates as male squirrels. •First tested external factors Found that dispersal was not caused by... aggression directed at
juvenile ground squires attempt to avoid their litter mates Tested by recorded observations or Then tested internal factors Hypothesis- Males stay close to home until they
reach a critical size at which point they disperse. Compaired their records of dispersion
to records of squirrle weight. Found Corilation Conducted lots of observatoin based tests. Found that food competition, parasite infestation, and availability of nests all had no barring on why only males disperse Only reasonable hypothesis was that ground squirrels leave to avoid mating with their close relatives In all their data colection never observed the mating of two members of the same litter. If squirrels don’t mate with members of their litter it
would be beneficial to move away from your family. Tested by looking back at phylogenetic relatives of grounds squirrels. This could show if dispersion was A) a developmental error B) a by-product of natural selection Conclusions!
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