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Taxonomy of the common dolphins of the eastern Pacific Ocean
Delphinus bairdii Dall is a species of dolphin distinct from D. delphis Linnaeus, with which it has usually been synonymized. D. bairdii has a longer rostrum relative to the zygomatic width of the skull; the ratio of these measurements falls at 1.55 or above for bairdii and 1.53 and below for delphis. In the eastern Pacific Ocean, D. bairdii is found in the Gulf of California and along the west coast of Baja California, Mexico; D. delphis is presently found in the waters off California. Until approximately the beginning of the present century, bairdii occurred farther north in the eastern Pacific Ocean, at least to the Monterey Bay area of California. Restriction of bairdii to more southerly waters, probably as an indirect result of a change in water temperature, may have permitted delphis to move into inshore Californian waters. The Pacific population of D. delphis has a somewhat shorter rostrum than the Atlantic population, and is perhaps subspecifically different. A thorough analysis of the entire genus Delphinus is needed before the relationship of all the populations can be understood and names properly applied.
The functional significance of movements and positions of the pinnae of the African Elephant, Loxodonta africana
Observations of wild African elephants ( Loxodonta africana ) in Uganda indicated that flapping and spreading the highly vascularized ears are probably important functions for heat dissipation. Ear flapping increased as ambient temperatures rose and decreased or ceased during cold or rainy weather. Rate of ear flapping was inversely related to wind velocity. Spreading the ears reduced ear flapping, particularly when an elephant faced downwind. Stimuli that elicited alertness, excitement, or hostility caused elephants to raise their heads and spread their ears widely and rigidly, and large elephants occasionally flapped their ears loudly and sharply. Flapping and spreading the ears for heat dissipation are generally not interpreted as danger signals by other elephants.
Relationships among three criteria of puberty in Peromyscus leucopus noveboracensis
No abstract available.
Observations on parturition and development in the Hoary Bat, Lasiurus cinereus
Large numbers of female Lasiurus cinereus migrate northward through New Mexico in the spring months. Small samples of these bats were taken during May and June, 1969. A study of these specimens has yielded the results detailed herein.
Home range, social behavior, and dominance relationships in the African unstriped ground squirrel, Xerus rutilus
A field study of home range, social behavior, and dominance relationships in the African unstriped ground squirrel, Xerus rutilus , was conducted in semi-arid bushland near Kibwezi, Kenya. Ground squirrels lived alone or in small groups in isolated burrow systems and had broadly overlapping home ranges. They were neither territorial or colonial. Home ranges were estimated by visual observation of marked animals and those of males were considerably larger (mean=7.01 hectares (ha); n=4) than those of females (mean=1.37 ha; n-6). A continuum of agonistic behavior ranging from threat to combat is described, although actual combat was rarely observed. Sexual behavior includes a stereotypical tail display by adult males. Dominance relationships, based on 542 observed encounters between marked individuals, include a consistent male dominance over females and a fairly constant linear hierarchy among all individuals with shared home ranges. Similarities in the behavior of African ground squirrels and tree squirrels ( Sciurus ) are discussed.
Nocturnal and seasonal activities of the pallid bat, Antrozous pallidus
Nocturnal and seasonal activities of pallid bats ( Antrozous pallidus ) were observed in central Arizona. The pallid bat night is characterized by two roaming periods with an intervening period of night roosting. Foraging pallid bats have a characteristic style of flight well suited to the taking of relatively large, substrate-roving or slow flying prey. After the initial foraging period pallid bats locate one another through vocal communication and gather in night roosting clusters where they enter torpor. Durations and scheduling of nocturnal activities vary seasonally. Cool months are characterized by smaller colonies of bats, greater fidelity to certain colony sites, slower and later emergence, briefer foraging periods and longer periods of night roosting. Up to 75 percent of the time spent away from diurnal retreats is devoted to night roosting in the autumn. Young are born in June, and during most of the summer adult males do not seem to occur sympatrically with females and young. Females and young appear to forage together in July and August, when little fidelity is shown to roosting sites, large colonies exist, emergence is faster and earlier, and more time is spent in foraging than in cooler months. In mid-August a postbreeding dispersal occurs. These activities and behaviors are discussed in terms of the energetic demands on the bats and the socialization of young.
Organochlorine insecticide residues in the free-tailed bat (Tadarida brasiliensis) at Bracken Cave, Texas
Fifty-nine free-tailed bats ( Tadarida brasiliensis mexicana ) were collected at Bracken Cave, Texas, and analyzed for organochlorine insecticides and polyehiorinated biphenyls (PCBs). Residues of DDE in the brain were greater in 12 young collected from the floor than in 15 young taken from the ceiling, but food deprivation, not higher residues in the brain, apparently caused young to fall. Among 18 pregnant females, residues of DDE and DDT were highest in yearlings. The first lactation by yearlings caused their residue loads to drop sharply. Thereafter, increasing age was accompanied by increasing residues but amounts generally did not exceed those in yearlings. Residue levels in embryos were a function both of levels in the female parent and degree of embryonic development. Residues accumulated rapidly in nursing young, and lactating females may excrete from 1.3 to 16.2 (mean = 4.3) micrograms of DDE in milk per day. Maximum individual residue loads may be attained toward the end of nursing, and mobilization of these residues during southward migration may subject Bracken Cave free-tails to maximum lifetime residues in the brain. Comparison of our data with residue data for the free-tail population at Eagle Creek Cave (Arizona) in 1970 produced the following conclusions: (1) residues of DDE appeared similar in pregnant females, embryos, lactating females, and fallen young for the two populations; (2) residues of DDT and dieldrin appeared greater in pregnant females at Bracken Cave; (3) DDE and DDT occurred at greater levels in guano samples from Bracken Cave. On this basis, the population decline observed at Eagle Creek Cave between 1963 and 1969 does not appear to be related to the residues observed in the 1970 samples taken from that cave.
Home range defense in the red fox, Vulpes vulpes L.
This paper describes the home range defense behavior observed when nonresident male red foxes were introduced into established home ranges of resident male-female pairs. In 12 observation periods, four intruders were introduced to each of three mated pairs which had been given three weeks to acclimate to a 4.05-hectare, fenced enclosure. The residents centered their activities around a natural den and the frequency of intruder-resident encounters decreased rapidly with increasing distance from the den. The primary home range defense was continual harassment of the intruders by the resident males through agonistic displays and chases. Physical contact was rare. Even though the resident males were dominant in less than a majority of the interactions observed, they were usually successful in displacing the intruders within a few hours. The resident females seldom interacted with the intruders.
Depredation of sea otter pups by bald eagles at Amchitka Island, Alaska
No abstract available.
Roosting ecology of the pallid bat, Antrozous pallidus
Daytime roosting behavior of pallid bats ( Antrozous pallidus ) was studied in central Arizona. Bats were present in the area from March or April until November and roosted in cliffs in colonies generally including 20 or more individuals. Pallid bats were highly selective in their choice of roost sites and minimized diurnal energy output by adaptive hypothermia and behavioral thermo-regulation. In spring and autumn the bats roosted in vertical crevices responsive to changes in ambient temperatures. Here temperatures remained low and the bats were torpid for much of the day, but when the crevices became heated in the late afternoon the bats were passively warmed prior to emergence. Deep, horizontal crevices were preferred in summer; cliffs function as massive heat sinks, and in summer crevice temperatures remained moderate and relatively stable. Throughout most of the day both the deep parts of the crevices and the body temperatures of the bats remained close to 30ºC; at this body temperature pallid bats have unexpectedly low metabolic rates (Trune, 1974). By adjusting their positions and closeness to other bats in the thermal gradient within the crevice, bats dissipate heat early in the day, maintain a low metabolic rate through most of the fat and elevate the body temperature prior to emergence in the evening. Of vital important to pallid bats in the summer are social behaviors that promote communal roosting at "traditional" crevices.
Establishment of the black-tailed jackrabbit on the Virginia eastern shore
No abstract available.
Weights, growth, and survival of timber wolf pups in Minnesota
Weights, growth rates, canine tooth lengths, and survival data were obtained from 73 wild wolf ( Canis lupus ) pups that were 8 to 28 weeks old when live-trapped in three areas of northern Minnesota from 1969 to 1972. Relative weights of wild pups are expressed as percentages of a standard weight curve based on data from captive pups of similar age. These relative weights varied greatly within litters, between litters, and between years; extremes of 31 to 144 percent of the standard were observed. Growth rates ranging from 0.05 to 0.23 kilograms per day were observed, and similar variations in general development and in replacement and growth of canine teeth were noted. Survival data based on radio-tracking and tag returns indicated that pups with relative weights less than 65 percent of standard have a poor chance of survival, whereas pups of at least 80 percent of standard weight have a high survivability. Pups born in 1972 were especially underweight, probably a result of declining white-tailed deer ( Odocoileus virginianus ) densities in the interior of the Superior National Forest study area.