Comparative Breeding Biology of Musk Shrews (Suncus murinus) from Guam and Madagascar

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Abstract
Breeding colonies of musk shrews (Suncus murinus) from the islands of Guam (G) and Madagascar (M) were maintained. Physical, physiological, and behavioral differences were observed between M, G, and “hybrid” (H, an offspring of a G/M mating) shrews. The shrews differed in appearance, body weight, and length. H males were longer than G and M males and heavier than G males; M females were heavier than G and H females. M shrews had significantly larger litters (2.8 ± 0.2 young per litter) and shorter gestation periods (29.6 ±0.1 days) than G shrews (2.1 ±0.1 young; 30.3 ±0.1 days). Nesting behavior occurred significantly more frequently in G shrews than M shrews (57.8 and 17.4 percent, respectively). Copulatory behaviors were significantly different between G and M shrews. G females were more aggressive than M females. Only M females showed lordosis during copulation. When G-M crosses were made, the differences in mating behavior interfered with successful completion of copulation. The percent of matings producing viable young was significantly reduced in G-M and H-H matings. Our data indicate that the reproductive isolation of the two island populations has allowed significant evolutionary changes to occur, which appear to be well on the way to creating two distinct species, suggesting that the taxonomic status of these two musk shrew populations should be reexamined.

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