Baiomys Taylori Research Articles

Some Aspects of the Reproductive Biology of Baiomys taylori ater

Some Aspects of the Reproductive Biology of Baiomys taylori ater

The effect of reciprocal cross fostering on the behaviour of two species of rodents, Mus musculus and Baiomys taylori ater

Summary 1. Four treatment groups were used: two control groups, Baiomys pups reared by Baiomys dams and Mus pups reared by Mus dams: two experimental groups, Mus and cross-fostered Baiomys pups reared by Mus dams, and Baiomys and cross-fostered Mus pups reared by Baiomys dams. The adult behaviours of control animals were compared to those of experimental conspecifics. 2. The open field total activity scores of cross-fostered Baiomys were greater than those of control Baiomys. The open field total activity scores of cross-fostered Mus were lower than those of control Mus. It is suggested that differential handling by the dams might account for this difference. 3. In a social preference test control Mus and Baiomys spent more time in a chamber adjacent to a conspecific. Both cross-fostered male and female Mus spent more time in a chamber adjacent to a Baiomys. However, the cross-fostered female Mus showed a stronger preference for the foster species than did the cross-fostered Mus males and cross-fostered male Baiomys spent more time adjacent to a conspecific. Thus the results from the social preference tests indicated that females were more affected by cross-fostering than males. 4. The behaviours of animals from control groups differed from those of the cross-fostered groups when pair encounters were staged between conspecifics and between Baiomys and Mus. Some of the differences involved measures of fighting and grooming behaviour, number of attempted mounts and approach and with-drawal behaviour. 5. Pair encounters revealed that the cross-fostered animals were reacting more positively to the foster species than to conspecifics. 6. Cross-fostered animals were profoundly influenced in their open field performances, social preferences (with the exception of the male cross-fostered Baiomys) and social behaviours as a result of being cross-fostered to a different species at birth. The cross-fostered animals established, presumably through learning, new social relationships with the foster species. 7. Cross-fostered male and female Mus did not lose their ability to mate with a conspecific. This implies that sexual behaviour in this species is less susceptible to change due to early experience than other social behaviours such as fighting, allogrooming, and approach and avoidance behaviours.

Development of metabolic response to cold in young mice of four species

1. 1. The species studied were: Baiomys taylori, 8 g mature wt; Perognathus longimembris, 10 g; Peromyscus maniculatus, 21·5 g; Mus musculus, 32 g. Metabolic rate of a litter was measured at 1–6-day intervals until it could maintain a “constant” increased metabolism for 1–1.5 hr at T a 20°C, the response here defined as homeometabolism. 2. 2. B. taylori and M. musculus showed no rise of metabolism at T a 20°C until 5–8 days old and 1 day old respectively. The initial ability to increase metabolism may depend on muscular movement in B. taylori, but it does not in the larger species. In all species the ability for sustained increase coincided with the first occurrence of obvious shivering and piloerection, and with 2–4 mm of underfur. 3. 3. The weight at which each species attained homeometabolism is directly related to mature weight, and the age at this time is inversely related to weight. Both a minimum body weight and a minimum time for development after birth are necessary for homeometabolism. 4. 4. B. taylori became homeometabolic at 2·4 g, which is the weight Pearson (1948) predicted as the minimum for homeothermy in mammals. 5. 5. In all species the average ml O 2·g −1 hr −1 at T a = 20°C and the minimum at 35°C both increased with growth, up to the point where they equalled adult values. These rates then declined with further growth. Maximum metabolic rate increased with growth to at least four to six times the adult basal rate.

Temperature Regulation and Torpidity in the Pygmy Mouse, Baiomys taylori

Temperature Regulation and Torpidity in the Pygmy Mouse, Baiomys taylori

A New Species of Flea from the Field Mouse, Baiomys Taylori

A large series of an apparently new flea has been taken from the field mouse, Baiomys taylori , in Lavaca County, Texas, in connection with an extensive murine typhus research program being conducted there by the Texas State Department of Health and the United States Public Health Service. Considering the small size of the Baiomys , the mice were heavily infested with this flea. During March and April, 1946, eighty-one fleas were combed from twenty-one of these mice.