1 / 30
2 / 30
3 / 30
4 / 30
5 / 30
6 / 30
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8 / 30
9 / 30
10 / 30
11 / 30
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13 / 30
14 / 30
15 / 30
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20 / 30
21 / 30
22 / 30
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29 / 30
30 / 30
This is due to a range of factors, including genetic incompatibility, physical barriers, and behavioral.