Three hundred and thirteen live specimens from 12 species and eight subspecies of Peromyscus were examined for the presence and size of a specialized midventral sebaceous area. External evidence of the area was found primarily in P. maniculatus and P. polionotus. No strong relationship was found between the habitat of the species and glandular presence or size. Glandular areas of males were usually larger than those of females from the same species. In males from a number of taxa examined, size of the glandular area correlated negatively with age. Histological analysis confirmed these general relationships in P. m. bairdii, and revealed that hair follicles were generally absent from the specialized area. In males of P. m. bairdii, androgen dependency of the sebaceous area was determined by castration and subsequent testosterone replacement. The glandular areas of ovariectomized female P. m. bairdii given estrogen and subsequent progesterone were markedly reduced in relation to those of oil-treated controls.
Reproductive parameters were assessed in populations of the roof rat (Rattus rattus) and the Polynesian rat (Rattus exulans) in Hawaii for 1 year as a step in understanding population regulation in these species. Populations of the roof rat undergo a yearly cycle in which density is highest and reproduction is lowest in the winter. During the second winter of this study, numbers did not return to previous high levels, yet reproductive activity was curtailed. This suggests that reproductive activity is controlled mainly by environmental factors rather than those that are density dependent. Density of the Polynesian rat was generally low in each study population. Populations of both species generally had low productivity in comparison to those in other geographical areas. This low productivity is brought about by altered life history components: delayed maturation, fewer litters per female, and fewer young per litter. This study is part of an effort to gather reproductive, demographic, and genetic data with the goal of elucidating the mechanisms of population regulation and the relationship of natural selection to population processes in these species.
Secretions from the gular gland of male molossid bats (Tadarida brasiliensis and Molossus bondae) and pararhinal glands of male big brown bats (Eptesicus fuscus) were analyzed histochemically. Proteins and phospholipids were apparently absent from secretions of the glands of all three species. Sebaceous portions of the gular gland of both molossids contained unsaturated neutral lipids; older secretion in distal portions of their ducts consisted of unsaturated neutral and acidic lipids. Cholesterol and its esters and carbohydrates were not detected in sebaceous cells of gular glands. Apocrine secretions from Molossus contained neutral lipids and carbohydrates.
Pararhinal glands from Eptesicus consisted of sebaceous and apocrine portions. The former contained neutral lipids and cholesterol esters throughout. Fatty acids were present in apical cells; unsaturated lipids were more prevalent in apical than in basal cells. Apocrine portions of pararhinal glands contained saturated fatty acids, but tests for carbohydrates, proteins, and phospholipids and cholesterol compounds were negative.
Histochemical results indicate that at least some of the ester molecules from sebaceous glands are hydrolyzed before release from the gland. Unsaturated, probably short-chain, fatty acids thus released are the most likely components responsible for the well-known odor of these secretions.
The retention of 65Zn and 54 Mn were measured in Peromyscus polionotus that were subjected to different ambient temperatures or to forced exercise. Food intake and assimilation were measured simultaneously with the excretion of the intraperitoneally injected isotopes. The mean elimination constant (k) for 65Zn of the exercised mice was significantly larger than that of the unexercised mice, although the metabolic rates of the two groups were not different. For the group retention curves, k for 65Zn, days 20 to 38, and the area under the curve, days 0 to 38, varied inversely with temperature. The average metabolic rate of a group of mice was significantly correlated with the area under the group curve (r = 0.96). The excretion of 54Mn did not vary significantly with temperature. Food intake, food assimilation, and metabolic rate of individual mice were highly predictable from multiple correlations with ambient temperature and body weight, which together accounted for 96 to 98 per cent of the variability. In only one case did a parameter of the zinc retention curve contribute more than an additional 2 per cent to the predictability of the multiple correlations. In terms of simple correlations, food intake, food assimilation, and metabolic rate of individual mice were significantly related to k for 65Zn, days 20 to 38, and to the area under the retention curve, but the predictabilities of the simple regressions were 58 per cent or less.
Examination of 712 specimens of Blarina brevicauda from widely separated localities revealed 48 dental abnormalities. Specimens having abnormal dentitions were x-rayed to determine whether or not injury was involved. Six kinds of abnormalities are discussed. Criteria for classifying specimens of B. brevicauda in age categories are established. Because subnumerary dentitions occur frequently in adults and old adults, it is reasoned that survival of specimens lacking unspecialized unicuspids is not prejudiced. Crowding of unicuspids probably is one cause of the tendency toward reduction in number of teeth in B. brevicauda, and this tendency is greatest in subspecies having small skulls.
Spectrophotometric measurements of preretinal absorbance were made on eyes from prairie dogs, western gray squirrels, four species of ground squirrels, and a southern flying squirrel. Results indicate that lenses from all species except the flying squirrel absorb significantly in the spectral region from 520 to 440 nanometers. At 440 nanometers, relative preretinal absorbance was greatest for the prairie dogs (1.31) followed in order by the ground squirrels (1.12 to 1.04), the gray squirrels (0.54), and the flying squirrel, which had an essentially transparent lens and cornea (0.08).
Altitudinal zonation studies of four species of giant rats in West Malaysia have shown that Rattus sabanus and R. muelleri are essentially lowland species, R. bowersii inhabits both lowland and highland forests, but R. edwardsi is confined to high elevations. It was found that R. edwardsi and R. sabanus are partially arboreal in habit and tend to prefer the drier parts (upland) of the forest, whereas R. bowersii and R. muelleri are strictly ground-dwellers. R. bowersii is equally common in both dry and wet habitats (near streams) in forests, whereas R. muelleri prefers wetter habitats. Analysis of stomach contents and laboratory feeding experiments were carried out to determine the natural diets and food preferences of these giant rats. Insects are taken by all four species, but particularly by R. sabanus and R. edwardsi. All eat some molluscs (especially R. muelleri ). R. muelleri also feeds on crabs, but the other three species apparently do not. R. bowersii is the most vegetarian. Data are presented on the endoparasite patterns of these giant rats and are discussed with respect to criteria for “ecological labelling” the relative incidence of nematode and cestode infestations appears to be associated with the frequency with which insects and other animal foods are taken.
Seasonal physiological responses to ambient temperature were determined in Sylvilagus audubonii at Tucson, Arizona. From winter to summer the thermoneutral zone of desert cottontails (700 grams) shifted upwards, basal metabolism decreased by 18 per cent, and standard metabolism decreased above thermoneutrality and increased below. Water loss during summer was higher than in winter below 30° C, began to increase at a higher ambient temperature, and rose less steeply. The per cent of metabolic heat production dissipated by evaporative heat loss did not change seasonally, and equalled 100 at an ambient temperature of 41.4° C. Body temperature was 38.3° C at ambient temperatures below 30° C, and did not differ seasonally. Hyperthermia began within thermoneutrality at a slightly higher ambient temperature during summer resulting in lower hyperthermic body temperatures. Body temperature equalled ambient at 41.9° C during summer and a predicted 42.9° C during winter. The dry heat transfer coefficient was higher during summer below 30° C but there was no apparent seasonal difference at higher ambient temperatures.
Sylvilagus audubonii survives in the desert by taking advantage of every possibility to minimize the heat load and water expenditure. A relatively high evaporative cooling capacity and high lethal body temperature of 44.8° C provides a safety factor for desert cottontails if avoidance is not possible.
The tyrosine content of eye lenses of known-age old-field mice (Peromyscus polionotus) were analyzed colorimetrically. The soluble fraction increases linearly with age from 45 to 308 days, but thereafter is not related to age. The insoluble fraction varies curvilinearly with age to at least 750 days. Accumulation of soluble protein represents growth, whereas conversion of soluble to insoluble protein is regarded as aging. Aging, as measured by the insoluble fraction, is much less variable than growth, and affords an age estimating technique with unprecedented accuracy for small mammals. The 95 per cent confidence limits about a predicted age of 100 days are 96 to 107 days for a mean prediction, 70 to 147 days for individual prediction. Similar values for 400 days are 390 to 426 and 285 to 583 days, respectively.
Hearing sensitivity and ultrasonic vocalization in glossophagine bats were investigated as they relate to an anatomical and behavioral continuum from insectivory to nectar and pollen feeding. The performance of four species in obstacle avoidance tests indicates that the more insectivorous members of the subfamily can detect wires of equivalent diameter to those reported for Myotis, whereas those bats which interact exclusively with chiropterophilous plants exhibit inferior performance. Hearing sensitivity as measured by cochlear potentials does not reflect the dietary habits, but supports a view of polyphyletic origin for the subfamily. The data suggest that although target detection depends on multiple factors, the sound-producing mechanism of these bats is more open to selective modification through ecological pressures than is the receiver.
A study of the diurnal activity pattern in relation to rank and social behavior was conducted just prior to the mating season in a free-ranging band of rhesus monkeys (Macaca mulatto) on Cayo Santiago, Puerto Rico. One hundred and thirty hours were spent observing the dominant, the fifth-ranking and the eleventh-ranking males of an adult male social hierarchy of 12 individuals. The three monkeys spent most of their time resting, feeding or grooming. Differences between monkeys based on individual characteristics and social rank are pointed out. Social encounters were frequent, but these occupied little of any monkey's time. In this study, activity patterns depended on a combination of individual characteristics, social rank and interaction with other individuals.
Adrenal weights were obtained for 662 Peromyscus leucopus noveboracensis and 281 wild Peromyscus maniculatus bairdii. The relationship of adrenal weight to body weight was explored using a number of parameters for size of the animals. The best linear fit for adrenal weight for both species was on body weight ,73, although this was only slightly better than for body weight 67. From these relationships it appears that adrenal weight is directly related to surface area and by inference to total metabolism and oxygen consumption. However, adrenal weights of P. m. bairdii are absolutely and relatively much less than those of P. leucopus and the rate of increase in adrenal weight with increasing body weight is much greater in leucopus. It is inferred that these differences reflect basic physiological and probably behavioral differences between these two species. There was no evidence of an increase in adrenal weight in females at maturity, thus raising questions concerning corticoid binding in these animals. Similarly, there was no suggestion of a rise (or fall) in the adrenal weight at maturity in males. Finally, it was suggested that in many instances adrenal weight provides a rapid and certain means for differentiating between P. leucopus and P. m. bairdii.
Body weights of Eutamias amoenus luteiventris (Allen) and Eutamias minimus oreocetes Merriam collected in western Alberta were low in April on emergence from hibernation and increased through May and June to a constant summer level. Adrenal weights were also low at the time of spring emergence but increased steadily, reaching a peak in July and August. In the case of breeding males, this seasonal increase in adrenal weight was delayed until the breeding season had ended but increase was rapid thereafter and relative adrenal weights of breeding males were comparable with those of the rest of the population by July. Limited data suggest a decrease in adrenal size before hiber¬nation. Seasonal changes in adrenal weight may be related to seasonal changes in social interaction but could just as readily be related to other seasonal variables such as reproduction, hibernation, food-gathering activity, length of foraging move¬ments, and density of vegetative cover.
Two hundred and thirty-two hamsters were subjected to varied social interactions and testosterone therapy. Body weight was an accurate predictor of social dominance in hamsters. Social rank significantly affected adrenal weight, width of the cortex, and ascorbic acid levels. Testosterone may act in conjunction with social rank to induce changes in adrenal morphology.
Adrenocortical hormones of Spermophilus beecheyi were determined in gland incubates and in plasma. Cortisol, corticosterone and aldosterone were found in that order of decreasing abundance in both gland incubates and plasma. Adrenal gland histology is essentially like that of S. beldingi (McKeever, 1963). Adrenal glands from males weigh more than those from females.
Forty-nine female and 32 male African elephants (Loxodonta africana) were collected from July 1958 to May 1959 in Bunyoro District, Uganda. Reproductive status, body weight, and measurements were recorded and ages estimated. Gross morphology and histology of the adrenal gland are described: histology of the elephant adrenal corresponds with generalized descriptions for those of other eutherian mammals. the fetal cortex is well developed in an elephant 2 months of age, but gradually degenerates and is completely absorbed by the fourth year of postnatal life without giving rise to another transitory zone. No significant increase in relative adrenal weight related to Uganda's December-to-March dry season was detected. Relative adrenal weight of elephants is higher in females than males of comparable age, in immature males than mature males, and in immature females than nonpregnant or nonlactating females. Pronounced increase in relative adrenal weight is related to pregnancy and lactation.
Weights were obtained and histological examinations made of the adrenal glands and reproductive organs of 193 female Microtus pennsylvanicus trapped on the grasslands of the Letterkenny Army Ordnance Depot in south central Pennsylvania. The relationships between adrenal weight and histology and reproductive status and population size were examined. Adrenal weight increased sharply at sexual maturity but there were no further changes in adrenal weight relative to body weight with changes in reproductive status once maturity was reached. It also was concluded that the inner juxtamedullary portion of the adrenal cortex of female voles is inner-fasciculata-reticularis and not an X-zone and that the adrenal hypertrophy at maturation is probably due to increased secretion of estrogens. There was marked and significant parallelism between mean adrenal weights and population size for mature females; but less so for immature females. Changes in adrenal weight, particularly in the mature females, were attributed to changes in population size and not to reproductive status or directly to seasonal environmental changes.
Grouped laboratory mice (Mus musculus) show higher adrenocortical function than isolates, and this is usually attributed to the occurrence of aggressive behavior in such groups. the present experiment compares the effects of controlled bouts of fighting on adrenocortical function in trained fighter and defeated male mice. the results revealed increased adrenal function (compared with isolated controls) only in the latter condition; it is therefore concluded that success in aggressive encounters, in contrast to defeat, does not contribute to the increased adrenocortical function found in grouped mice.