Effects of adults on survival and recruitment of Peromyscus leucopus

1987 ◽  
Vol 65 (10) ◽  
pp. 2519-2523
Author(s):  
Gregory H. Adler ◽  
Mark L. Wilson ◽  
Michael J. DeRosa
Keyword(s):  
Adult Female ◽  
Adult Male ◽  
Peromyscus Leucopus ◽  
Survival Rates ◽  
Adult Males ◽  
Control Grid ◽  
Young Males ◽  
Young Females ◽  
Breeding Seasons ◽  
And Control

A population of Peromyscus leucopus (white-footed mouse) in northeastern Massachusetts was manipulated for 3 years to determine the effects of adults on survival and recruitment. Two experimental grids were established, from which either all adult males or all adult females were removed continually. The effects of these two manipulations were compared with demography on a control grid. Manipulations had no apparent effect on breeding intensity of young, survival rates of adults, or residency rates of adults and young. Recruitment of adult males was higher on the adult male removal grid than on the control grid. Recruitment rates of adult males and of young males and young females were lower on the adult female removal grid than on the control grid. Survival rates of young males were higher on the adult female removal grid than on the control grid; this effect may have been due to either reduced adult female residency or adult male recruitment. All differences between experimental and control grids were noted only during breeding seasons. Adult males apparently limited recruitment of adult consexuals. The effects of manipulations on other measured parameters were inconclusive because of high immigration rates of adult males onto the adult male removal grid and reduced recruitment of adult males and decreased production of young on the adult female removal grid.

Survival rates of radio-collared female polar bears and their dependent young

1995 ◽  
Vol 73 (7) ◽  
pp. 1312-1322 ◽  
Author(s):  
S. C. Amstrup ◽  
G. M. Durner
Keyword(s):  
Adult Female ◽  
Survival Rates ◽  
Beaufort Sea ◽  
First Year ◽  
Human Populations ◽  
Polar Bears ◽  
Adult Males ◽  
Kaplan Meier ◽  
Second Year ◽  
Sea Survival

Polar bears (Ursus maritimus) are hunted throughout most of their range. In addition to hunting, polar bears of the Beaufort Sea region are exposed to mineral and hydrocarbon extraction and related human activities such as shipping, road building, and seismic testing. As human populations increase and demands for polar bears and other arctic resources escalate, reliable estimates of survivorship of polar bears are needed to predict and manage the impacts of those activities. We used the Kaplan–Meier model to estimate annual survival (with 95% confidence intervals) for radio-collared female polar bears and their dependent young that were followed during a 12-year study in the Alaskan Beaufort Sea. Survival of adult female polar bears was higher than had been previously thought: Ŝ = 0.969 (range 0.952–0.983). If human-caused mortalities were deleted, the computed survival rate was 0.996 (0.990–1.002). Survival of young from den exit to weaning was 0.676 (0.634–0.701). Survival during the second year of life, 0.860 (0.751–0.903), was substantially higher than during the first year, 0.651 (0.610–0.675). Shooting by local hunters accounted for 85% of the documented deaths of adult female polar bears. Conversely, 90% of documented losses of young accompanying radio-collared females were not directly caused by humans. Deaths of dependent young were independent of litter size (P = 0.36), indicating that parental investment in single cubs was not different from investment in litters of two or more. Precise estimates of the survival of independent juveniles and adult males still need to be developed.

Effects of age and photoperiod on reproduction and the spleen in the marsh rice rat (Oryzomys palustris)

2001 ◽  
Vol 280 (4) ◽  
pp. R1249-R1255 ◽  
Author(s):  
Kent E. Edmonds ◽  
Milton H. Stetson
Keyword(s):  
Adult Male ◽  
Reproductive Organ ◽  
Spleen Weight ◽  
Adult Males ◽  
Young Females ◽  
Reproductive Response ◽  
Body Weights ◽  
Marsh Rice Rat ◽  
Oryzomys Palustris ◽  
Older Males

To examine the interactions between age and photoperiod on reproduction and spleen weights, we exposed adult male and female rice rats of various ages to photoperiods of 16:8-h light-dark photoperiods (16L:8D) or 12L:12D. After 10 wk, animals were killed and the following data were recorded: weights of testes, seminal vesicles, uterus, ovaries, body, and spleen and, in addition, vaginal patency. Young adult males displayed a greater degree of testicular and seminal vesicle regression in short photoperiods than did older males; the testes of most older males did not regress in response to short photoperiods. Spleen weight was unresponsive to short photoperiods in all males, but was affected by age. Females, however, exhibited reproductive organ regression and decreased vaginal patency in response to short photoperiods at all ages examined. Body weights were affected by photoperiod in young females, and, as in males, photoperiod had no effect on spleen weights. These data suggest that the reproductive response to photoperiod in adult male rice rats declines with age, whereas in adult females it does not.

ADRENAL WEIGHT IN WILD MALLARD AND DOMESTIC DUCKS AND SEASONAL ADRENAL WEIGHT CHANGES IN THE MALLARD

1965 ◽  
Vol 43 (3) ◽  
pp. 475-487 ◽  
Author(s):  
E. O. Höhn ◽  
A. K. Sarkar ◽  
A. Dzubin
Keyword(s):  
Sex Differences ◽  
Breeding Season ◽  
Adult Female ◽  
Adult Male ◽  
Adrenal Weight ◽  
Adult Males ◽  
Weight Changes ◽  
Domestic Ducks ◽  
Testicular Weight ◽  
Wild Mallard

Mallards and domestic ducks are conspecific. Relative adrenal weight is similar in newly hatched mallards and domestic ducks. Immature mallards have higher relative adrenal weights than domestic ducks of similar age. Adult female mallards also have higher relative adrenal weights and a higher proportion of cortex in the adrenal than adult female domestic ducks, but adult males of the two strains fail to show these differences.Adrenal weight is related to testicular weight in mallards and domestic ducks, but no correlation is evident between adrenal weight and weight of the ovary and oviduct in mallards. Mallards show no adrenal weight sex differences at any of the three ages sampled. A seasonal adrenal weight cycle is apparent in both sexes of the mallard with a weight increase related to the breeding season and another increase during the autumn and winter.The higher relative adrenal weights of (immature and adult female) mallards compared to those of domestic ducks are attributed to the mallards' greater exposure to stress. It is suggested that this effect operates also in adult male mallards but is obscured in the comparison with adult male domestic ducks because in the latter, which have much higher testicular weights, another factor responsible for the correlation between adrenal and testicular weight as noted above makes for increased adrenal weights.

scholarly journals Reproductive seasonality, sex ratio and philopatry in Argentina's common vampire bats

2017 ◽  
Vol 4 (4) ◽  
pp. 160959 ◽  
Author(s):  
H. A. Delpietro ◽  
R. G. Russo ◽  
G. G. Carter ◽  
R. D. Lord ◽  
G. L. Delpietro
Keyword(s):  
Specific Information ◽  
Adult Males ◽  
Reproductive Seasonality ◽  
Tropical Regions ◽  
Young Males ◽  
Young Females ◽  
Vampire Bats ◽  
Lactating Females ◽  
Free Ranging

Common vampire bats ( Desmodus rotundus ) are a key rabies vector in South America. Improved management of this species requires long-term, region-specific information. To investigate patterns of demography and dispersal, we analysed 13 642 captures of common vampire bats in Northern Argentina from the period 1969–2004. In contrast with findings from more tropical regions, we found reproductive seasonality with peak pregnancy in September and peak lactation in February. Curiously, sex ratios were consistently male-biased both in maternity roosts and at foraging sites. Males comprised 57% of 9509 adults caught at night, 57% of 1078 juveniles caught at night, 57% of 603 juveniles caught in roosts during the day, and 55% of 103 newborns and mature fetuses. Most observed roosts were in man-made structures. Movements of 1.5–54 km were most frequent in adult males, followed by young males, adult females and young females. At night, males visited maternity roosts, and non-pregnant, non-lactating females visited bachelor roosts. Males fed earlier in the night. Finally, we report new longevity records for free-ranging vampire bats: 16 and 17 years of age for a female and male, respectively. Our results are consistent with model predictions that sex-biased movements might play a key role in rabies transmission between vampire bat populations.

EFFECT OF SEX AND AGE AT GONADECTOMY ON THE SEBACEOUS RESPONSE TO PROGESTERONE

1977 ◽  
Vol 73 (1) ◽  
pp. 67-70 ◽  
Author(s):  
SAM SHUSTER ◽  
WENDY M. HINKS ◽  
A. J. THODY
Keyword(s):  
Adult Female ◽  
Adult Male ◽  
Female Rats ◽  
Male Rats ◽  
Adult Males ◽  
Adult Rat ◽  
Sebum Production ◽  
Males And Females ◽  
Sebum Secretion

SUMMARY The effect of progesterone on the rate of sebum secretion was examined in intact and gonadectomized rats. In intact, adult, male rats, progesterone administered for 3 weeks decreased sebum secretion; after castration of adult males, progesterone increased sebum secretion and an even greater response occurred in males castrated at 21 days of age. In intact, adult, female rats progesterone slightly increased sebum production. As in the male, the response was affected by the time of gonadectomy, a greater response occurring after spaying at 21 days compared with 10 weeks of age. Thus, the response to progesterone in the adult rat differs in intact males and females and is affected by changes in the endocrine environment induced by gonadectomy, especially near the time of puberty.

Factors Affecting the Distribution of Mallards Wintering in the Mississippi Alluvial Valley

The Auk ◽  
1983 ◽  
Vol 100 (4) ◽  
pp. 932-946 ◽  
Author(s):  
James D. Nichols ◽  
Kenneth J. Reinecke ◽  
James E. Hines
Keyword(s):  
Population Size ◽  
Mississippi Alluvial Valley ◽  
Adult Males ◽  
Alluvial Valley ◽  
Factors Affecting ◽  
Young Males ◽  
Young Females ◽  
Winter Distribution ◽  
Wintering Areas ◽  
Males And Females

Abstract The Mississippi Alluvial Valley (MAV) is the principal wintering area for Mallards (Anas platyrhynchos) in the Mississippi Flyway. Here, we consider it a distinct habitat (sensu Fretwell 1972), i.e. fitness is relatively homogeneous among ducks within the MAV but different from that of ducks in other such habitats. We analyzed recovery distributions of Mallards banded preseason (July-September 1950-1980) to test hypotheses concerning the effects of winter temperatures, precipitation, and population levels on Mallard winter distribution. When two groups of years that comprised extremes of warm and cold winter weather were compared, recovery distributions of all four age and sex classes (adult males and females, young males and females) differed significantly; recoveries were located farther south in cold years. Recovery distributions also differed between wet and dry years in the MAV for all groups except adult males, higher proportions of recoveries of adult females and of young males and females occurring in the MAV during wet winters. Although differences in continental Mallard population size were associated with differences in recovery distributions only of adult males and young females, the proportion of young males and of all young Mallards recovered in the MAV increased during years of low populations. We conclude that temperature, water conditions, and population size affect the habitat suitability of Mallard wintering areas and that Mallards exhibit considerable flexibility in winter distribution associated with these factors.

Benefits, Costs, and Determinants of Dominance in American Black Ducks

Behaviour ◽  
1989 ◽  
Vol 109 (3-4) ◽  
pp. 222-234 ◽  
Author(s):  
Gary R. Hepp
Keyword(s):  
Body Mass ◽  
Dominance Rank ◽  
Positive Association ◽  
Adult Males ◽  
Restricted Diet ◽  
Significant Positive Association ◽  
Young Males ◽  
Young Females ◽  
American Black ◽  
Ad Libitum

AbstractBehavioural dominance was studied in captive American black ducks (Anas rubripes) during October-December 1984. Eighty ducks were marked individually, and groups of 10 ducks consisting of 5 adults (3 males and 2 females) and 5 juveniles (3 males and 2 females) were assigned to each of 8 experimental pens. Ducks in 4 pens received an ad libitum diet, and ducks in the other 4 pens were given a restricted diet. Dominance structure within pens was linear. Adults were dominant to young, and body mass had no influence on dominance rank. The effect of sex on dominance rank was age-specific. Adult males were dominant to adult females and to young black ducks of both sexes; however, dominance rank of young males did not differ from adult or young females. Paired adults were dominant to unpaired adults and to young individuals that were either paired or unpaired. Paired young black ducks were similar in dominance rank to unpaired adults and unpaired young indicating that pairing did not make these individuals more dominant. Ducks on the restricted diet gained less body mass than ducks on the ad libitum diet (HEPP, 1986), but dominant and subordinate black ducks within treatment groups experienced similar changes in body mass during the early winter. Dominant black ducks interacted more frequently and were more likely to form pair bonds than subordinates, thus higher energy costs of dominant individuals may explain the poor relationship between physical condition and dominance rank. There was a significant positive association between the dominance ranks of pair members.

Dispersion of adult male Peromyscus leucopus in relation to female reproductive status

1989 ◽  
Vol 67 (4) ◽  
pp. 1047-1052 ◽  
Author(s):  
Xuhua Xia ◽  
John S. Millar
Keyword(s):  
Mating System ◽  
Adult Male ◽  
Early Pregnancy ◽  
Peromyscus Leucopus ◽  
Natural Populations ◽  
Negative Relationship ◽  
Late Pregnancy ◽  
Adult Males ◽  
Adult Females ◽  
Female Reproductive Status

We studied dispersion of adult male Peromyscus leucopus in relation to the stage of pregnancy of adult females in natural populations monitored with Longworth live traps. Because postpartum mating is common in P. leucopus and days to parturition measures how far a female is from her next mating, we predicted that a female in early pregnancy (many days to parturition) would have fewer adult males in her neighbourhood than a female in late pregnancy (few days to parturition). Number of adult males caught within 30 m of each adult female was recorded and number of days to parturition for each female was obtained by bringing females back to the laboratory and allowing them to give birth. A negative relationship was found between number of adult males in a female's neighbourhood and days to parturition of the female (r = −0.419, p < 0.01), with the latter accounting for 8.8% of the variance in the former. These results support the hypothesis of a promiscuous mating system in P. leucopus.

A Previously Unknown Plumage of First-Year Indigo Buntings and Theories of Delayed Plumage Maturation

The Auk ◽  
1986 ◽  
Vol 103 (2) ◽  
pp. 281-292 ◽  
Author(s):  
Sievert Rohwer
Keyword(s):  
The United States ◽  
The Body ◽  
First Year ◽  
Adult Males ◽  
Young Males ◽  
Young Females ◽  
Female Mimicry ◽  
Breeding Plumage ◽  
Almost All ◽  
Wintering Ground

Abstract First-year, but not adult, Indigo Buntings (Passerina cyanea) have a previously unknown supplemental plumage. The presupplemental molt includes all of the rectrices, the outermost but not the innermost primaries, and, typically, the three innermost secondaries and all body feathers. In this molt, young females exchange one adult-femalelike plumage for another, while young males exchange an adult-femalelike plumage for one that matches that of adult males in winter. Thus, in their first year Indigo Buntings wear: first, the juvenile plumage, the body feathers of which begin replacement before the tail is fully grown; second, the first basic plumage, which in both sexes is entirely femalelike in coloration and includes the juvenile remiges and rectrices; third, the supplemental plumage, assumed either prior to fall migration (<10% of individuals) or on the wintering ground (>90% of individuals) and in which obvious sexual dichromatism is first achieved; and fourth, the first alternate plumage, acquired in a prolonged and often incomplete prealternate molt of body feathers that occurs during February, March, and April on the wintering ground and during the spring in the United States. Because almost all of the femalelike first basic plumage of young males is lost in the presupplemental molt, this plumage almost certainly is an adaptation to conditions encountered either in the fall or early in the first winter. Furthermore, the ensuing supplemental plumage cannot be compromised by color requirements of the first breeding season because of the intervening prealternate molt; thus, the adult-malelike plumage produced by the presupplemental molt likely evolved to meet a change in signaling requirements that occurs in early winter. The signaling function of this plumage is unknown. Because this supplemental plumage of young males resembles the winter plumage of adult males and because all feathers grown by young males in their first prealternate molt resemble those of the adult male breeding plumage, the female mimicry hypothesis of Rohwer et al. (1980) is untenable for the subadult breeding plumage of yearling male Indigo Buntings.

Short-term association patterns of humpback whale (Megaptera novaeangliae) groups on their feeding grounds in the southern Gulf of Maine

1991 ◽  
Vol 69 (12) ◽  
pp. 3005-3011 ◽  
Author(s):  
Mason T. Weinrich ◽  
Anne E. Kuhlberg
Keyword(s):  
Group Size ◽  
Adult Female ◽  
Adult Male ◽  
Gulf Of Maine ◽  
Humpback Whale ◽  
Distinct Pattern ◽  
Megaptera Novaeangliae ◽  
Adult Males ◽  
Feeding Ground ◽  
Social Nature

Humpback whale (Megaptera novaeangliae) feeding ground associations show a distinct pattern of group size and composition. Median group size was 2 (mean 1.67), and frequency decreased as group size increased. Adult females and juvenile males were observed in pairs significantly more often than singly, whereas adult males and juvenile females were more often alone. Adult female–female pairs occurred significantly more frequently than adult male–male pairs, and adult female – juvenile male pairs formed more frequently than adult male – juvenile female pairs. The majority of groups remained associated for at least 10 min; however, as the size of a group increased, so did its tendency to separate within that period. Adult male–male pair associations were of significantly shorter duration than female–female or male–female pair associations. It is hypothesized that adult males may avoid other males on the feeding ground as an extension of breeding competition. The energetic burden of reproduction, and hence the need to forage cooperatively to maximize efficiency, may account for the adult female's social nature. Juveniles of both sexes, less constrained by reproductive costs, exhibit less structured social behavior.

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