Isolated by behaviour

An animal's reproductive behaviour can isolate it just as effectively as physical barriers. Animal populations that develop different courtship patterns, breeding times or breeding places may also become cut off from others of their kind.

Water is no barrier to the Ipswich Sparrow, which spends summers on Sable and winters in New England. But Ipswich Sparrows breed only on Sable Island, and have become different from their parent stock, the Savannah Sparrow.

	What differences can you see?
Ipswich Sparrow Passerculus sandwichensis princeps		Savannah Sparrow Passerculus sandwichensis sandwichensis

Compare the size, tail length, overall colour, and the yellow patch in front of the eye.

Many small populations of Harbour Seals live along the North Atlantic coast. Sable's Harbour Seals have a strong tendency to return to the island to breed, instead of mixing with other Harbour Seals.

Harbour Seal -Anticosti Island	Harbour Seal - Sable Island
Phoca vitulina

Harbour Seal - Anticosti Island

Harbour Seal - Sable Island

Some features that are not common among Harbour Seals are becoming unusually frequent in Sable's population. For example, count the molar teeth on the seal skulls; most Harbour seals have 5.