摘要:

We analyzed the costs and benefits of natal dispersal and philopatry in a free-living population of the prairie vole,Microtus ochrogaster, in which 70% of the males and 75% of the females were philopatric. Rather than settling into a nest, 40% of male dispersers continued to wander throughout the study area, while only 13% of female dispersers did so. Whereas males were more likely to wander in spring-early autumn during low density periods, females were more likely to wander during spring-early autumn, irrespective of population density. Of those animals that settled into a nest, females were more likely than males to settle as single individuals. Same-sex siblings that dispersed commonly joined the same social group. Although often settling within 5 m of each other, opposite- sex siblings that dispersed never joined the same social group or formed a male-female pair. Total length of life was longer for males and females that dispersed than for those that remained at the natal nest. Animals survived longer after dispersal if they settled ≥ 30 m from the natal nest than if they settled ≤ 30 m from the natal nest. Length of survival following dispersal was not correlated with age at time of dispersal. Fitness of female dispersers was 2.5 times that of philopatric females, estimated by comparison of the percent becoming reproductive, survival time after becoming reproductive, and the estimated number of female offspring per litter that survive to adult age. The success of dispersers may be related to the high food resource habitat in which the study was conducted.

ISSN:0394-9370    

DOI:10.1080/08927014.1994.9522980

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Food-pass consists of the offering of food, mainly by males to females, in its two main forms: ground and aerial food-pass. The display is performed by all the harriers also in a ritualized form: flight-play, during which prey is not passed. These displays, which constitute the most frequent behaviour pattern inCircus pygargusduring the breeding period, are analyzed quantitatively and qualitatively in this work.

ISSN:0394-9370    

DOI:10.1080/08927014.1994.9522981

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Parent-offspring interactions during the rearing period were studied in the Pallid Swift, to examine competition for food among nestlings of different ages. We videotaped 1572 feeding events, in 26 nests over a period of 2 years.

ISSN:0394-9370    

DOI:10.1080/08927014.1994.9522982

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A population of 266 Cuvier's gazelles, descendants of two males and two females from the Western Sahara and living in the Estación Experimental de Zonas Aridas, was analyzed. Results show that the energy cost of producing and rearing offspring, measured as offspring body weight, does not vary between males and females. But more males than females die during the 1st month of life. The advantages of producing one or the other sex are discussed. The cost of the parents' future reproductive success of producing male or female offspring was also investigated. Interbirth intervals following a twin male-female birth are longer than the other possibilities. However, no effects were observed of sex and litter size of the previous birth on sex and litter size of next birth nor on survival to 1 month of the next birth. Also no relationships were observed when we compared the components of the lifetime reproductive success of mothers (mother's longevity, fecundity, 1 month survival rate, abortion rate and age at first birth) and the sex ratio of their progeny, except that primiparous females that delay breeding produce more males than females during their lifespan.

ISSN:0394-9370    

DOI:10.1080/08927014.1994.9522983

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

In animals that defer reproduction until after physiological maturity because of competition by older individuals, one would expect that individuals reproduce earlier when competition decreases. We investigated nine behaviours relevant to reproduction in subadult wood bison males in captivity where mature males have been experimentally removed and compared them to males in a control and a free ranging population. Free-ranging males fed less and walked more with increasing age. Mature males had more back-fat than subadults and they lost most of their fat during the rut. In the captive population, subadults in absence of mature males tended to feed less and were involved in more sexual and aggressive interactions than subadults in a control situation. They significantly increased feeding time from rut to late-rut, while in the control situation neither subadults nor mature males changed. However, the population's agestructure did not affect the pattern of subadults associating with cows, nor did it affect the length of tending bouts by subadults. Our results suggest that subadults can alter some reproductive behaviours depending on the social environment, but without taking on the role of mature males. The finding that some behaviours vary with the social environment while others do not has two implications for studies on reproductive behaviour: (i) researchers are advised to consider potential effects of the age-structure on observed behaviour, and (ii) the kinds of behaviours chosen to study should be considered relative to the potential effects of the age-structure.

ISSN:0394-9370    

DOI:10.1080/08927014.1994.9522984

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

From 1985 through 1990, I monitored the populations of two species of toads,Bufo quercicusandB. terrestris, at a temporary pond in the xeric uplands of north-central Florida. A drift fence with pitfall traps completely encircled the pond basin; the fence was monitored 5 days per week throughout the year. The 5-year study coincided with a severe regional drought that resulted in generally short hydroperiods at unpredictable times of the year. More than 800 toads were captured. Successful metamorphosis never occurred at the pond although toads continued to visit it throughout the study. The sex ratio was male biased inB. quercicusbut not inB. terrestris, although significant variation was observed from one year to the next. Likewise, the size-class structure and length-weight patterns varied among species, sexes, and years. Although fewer toads entered the pond basin as the study progressed, toads may have gone elsewhere to breed or they may have remained in refugia. Thus, decreased capture does not necessarily indicate that a drought-related population decline occurred. Drought may have disrupted normal arrival patterns and length of stay within the pond basin. Drought also could be responsible for variation in annual size-class structure of captured toads. The uncertainty of the hydroperiod both spatially and temporally in adjacent breeding sites, the ability of toads to move long distances with the potential for migration between breeding sites, and the lack of specificity in the choice of breeding sites (i.e. permanent versus different types of temporary wetlands) may lead to the formation of metapopulations in the xeric upland habitats of north-central Florida. Long-term monitoring under a variety of climatic conditions is needed to assess the effects of drought and other types of environmental stresses on toad populations.

ISSN:0394-9370    

DOI:10.1080/08927014.1994.9522985

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Honest advertisement models of sexual selection have been widely discussed as hypotheses for the evolution of ornament traits but, as previously formulated, these models lack a mechanism for the elaboration of display characters. I propose that female demand for display characters that reliably signal male quality leads to selection for male strategies to express these display characters independent of quality. The result can be an evolutionary race leading to the elaboration of male characters while maintaining a correlation between character expression and male quality. Extreme elaboration of display traits will occur only if males are able to adopt strategies that reduce the cost of character expression; otherwise, simple or moderately elaborated traits can remain reliable indicators of male quality indefinitely. Several display traits such as pheromone signals and carotenoid pigmentation of the integument are often found with associated structures that may have evolved through sexual conflict of interest.

ISSN:0394-9370    

DOI:10.1080/08927014.1994.9522986

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

AdultPortia labiatafemales are highly cannibalistic jumping spiders (Salticidae). The ability ofP. labiatafemales to discriminate between their own draglines and those of other conspecific females is investigated experimentally.P. labiatafemales consistently spend more time walking on their own draglines than those of other conspecific females.

ISSN:0394-9370    

DOI:10.1080/08927014.1994.9522987

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The blue petrelHalobaena caeruleais a nocturnal burrow-dwelling seabird: probably for this reason, sexual signalling in this species is based primarily on vocalizations. In this paper, we examine the possibility that structural parameters of the male call can provide information to females about male qualities. Several temporal parameters (durations and rhythm) are significantly correlated with body mass or condition of the males. These results are discussed in relation to the fact that body mass may be a good predictor of breeding success in some species of seabirds.

ISSN:0394-9370    

DOI:10.1080/08927014.1994.9522988

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor