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13y ago
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12y ago

So why is it that these apparently similar species cannot live together? John Gurnell of the Mammal Society believes that, "while there is no evidence that grey squirrels aggressively chase out red squirrels, or that grey squirrels brought a disease with them from North America that effect red squirrels, there can be no doubt that if the grey squirrel had not been introduced to Britain then the red squirrel would still be common in our parks and woodlands" (Gurnell, 2004).

When the ecology of each species is compared, the reasons for the dominance of the grey squirrel over the red become all too apparent. Grey squirrels can weigh as much as 600 grams, twice that of an adult red squirrel, and live for an average of 7-9 years, compared to 6-8 years for reds. They therefore have a significant physical advantage over the red squirrel. In addition, having evolved in the oak and hickory forests of the north-eastern United States, grey squirrels also have several behavioral advantages over reds (Gurnell, 1996; Gurnell et al., 2004; Kenward et al., 1998).

Unlike the red squirrel, which is primarily arboreal and spends only 33% of its time on the ground, the grey squirrel spends up to 80% of its time foraging on the woodland floor. This adaptation means that, in the autumn, grey squirrels can increase their body weight by as much as 20% while reds, which feed far less efficiently in broadleaved woodland, rarely manage to gain 10% (Kenward et al., 1998).

As neither grey nor red squirrels hibernate and both are therefore active throughout the winter months periods of extreme weather, when they are forced spend several days in the drey without feeding, can have severe consequences for the red squirrel, which cannot store as much fat as the grey. This deficiency is reflected in the fact that only 80% of young red squirrels survive their first winter and mortality remains as high as 50% in adults (Gurnell, 1994). The discrepancy between the feeding efficiency of the two species, particularly in broadleaved woodland, is further highlighted by the difference in the carrying capacity of this habitat for the two species. For red squirrels this is around 1-2 per hectare, while for greys it can be as high as 5 or even 6 per hectare (Gurnell, 1994).

Another important effect of these behavioral differences is that, while the dispersal of red squirrels is severely hampered in fragmented woodland where the tree canopy is broken, the grey can both forage over a wider area and find new territory more easily (Bryce et al., 2002). This has important implications for both red squirrel conservation and grey squirrel control and is accentuated in a habitat where human impacts such as woodland habitat destruction and fragmentation are also occurring.

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6y ago

no one knows but i like squirrels very much. i also like dogs. and cats. and horses. basicaly animals in general.

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Q: When were the gray squirrel introduced into the UK?
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