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Winter aggregations, Dehnel effect, and habitat relations in the Suisun shrew Sorex ornatus sinuosus

100%

Hays W. S. T., Lidicker W. Z.

Acta Theriologica

2000

tom 45

nr 4

A live-trapping study on Suisun shrews Sorex ornatus sinuosus Grinnell, 1913, an endangered subspecies, was performed during the non-breeding season along the edge of a tidal marsh in California. During the winter, these shrews lived in distinct social aggregations composed of a single adult male, several adult females, and subadults. These groups remained stable even when the adult male died. As the breeding season approached, these groups were invaded by numerous adult males resulting in a nearly complete change in group membership. At the end of the breeding season, adult body mass declined by 30 to 40% (Dehnel Effect), Shrews reached high densities along the marsh/grassland ecotone, but the precise locations of social groups seemed unrelated to the presence of particular plant species or to the amphipod food supply. Subadult males wintered mostly outside of social groups in the marsh below high tide level. Conservation efforts need to locus on preserving the tidal marsh ecotone without promoting contact wilh the upland subspecies.

Factors influencing the variation in capture rates of shrews in Southern California, USA

67%

Laakkonen J., Fisher R. N., Case T. J.

Acta Theriologica

2003

tom 48

nr 2

We examined the temporal variation in capture rates of shrews Notiosorex crawfordi (Coues, 1877) and Sorex ornatus (Merriam, 1895) in 20 sites representing fragmented and continuous habitat in southern California, USA. In N. crawfordi, the temporal variation was significantly correlated with the mean capture rates. Of the 6 landscape variables analyzed (size of the landscape, size of the sample area, altitude, edge, longitude and latitude), sample area was positively correlated with variation in capture rates of N. crawfordi. In S. ornatus, longitude was negatively correlated with variation in capture rates. Analysis of the effect of precipitation on the short- and long-term capture rates at 2 of the sites showed no correlation between rainfall and capture rates of shrews even though peak number of shrews at both sites were reached during the year of highest amount of rainfall. A key problem confounding capture rates of shrews in southern California is the low overall abundance of both shrew species in all habitats and seasons.

Ograniczanie wyników

2 Acta Theriologica

1 Case T. J.

1 Fisher R. N.

1 Hays W. S. T.

1 Laakkonen J.

1 Lidicker W. Z.

1 2003

1 2000

Wyniki wyszukiwania

Winter aggregations, Dehnel effect, and habitat relations in the Suisun shrew Sorex ornatus sinuosus

Factors influencing the variation in capture rates of shrews in Southern California, USA