摘要:

The reproductive biology of the wild boar was analyzed during a period of drought in a Mediterranean area, Doñana National Park (Spain), during 1993 and 1994. Births were highly synchronized, most of them occuring between February and April. The average litter size for litters of about 1 week of age was 3.05 piglets per birth. This figure is below most reported for other populations of the species which are mostly intrauterine litters, hence without the effect of perinatal mortality. The percentage of breeding adult females was below 17%, much smaller than that found for most Mediterranean areas. These results stress the breeding decision of females, rather than the timing of reproduction or the size of litters, as the main adjustment of reproductive effort in the wild boar under drought conditions, which may be common in fluctuating Mediterranean climates.

ISSN:0394-9370    

DOI:10.1080/08927014.2000.9522791

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Notwithstanding the important role of male harassment of females for theories of the evolution of mating systems, accurate estimates of its frequency and costs are available for only a few species. In this paper, we quantify the frequency of harassment in southern elephant seals, compare occurrences of harassment inside and outside harems, and estimate the costs of harassment in two populations at Sea Lion Island (Falkland Islands) and Punta Delgada (Valdés Peninsula). Southern elephant seal males are much larger than females, have enlarged canines, and are much more agile on land; hence, females have a small probability of escape from approaching males and may suffer intense molestation. Most males had limited access to females due to the despotic mating system, and their libido was high. Females were approached by males at high frequency, mostly when out of oestrus. The harassment level was negatively related to the ratio of breeding females to breeding males, and females breeding at the peak of the season suffered a lower level of harassment. Females of large harems were harassed less, and their likelihood of interact with secondary males was lower. The activity of harem females was less disrupted, and females in large harems had a higher proportion of resting time. Isolated females suffered more herding episodes, and were approached more frequently by secondary males. The main short-term cost of harassment was disruption of the females' activity schedule; harassment level and total active time were positively related. Suckling bouts were rarely interrupted by male harassment. Mother and pup separations caused by males interaction were rare, short-lasting, and rarely permanent. There was little effect of harassment on weanling weight, physical damage of females was rare, and there was only a slight non-significant negative relationship between harassment level during one season and the likelihood of surviving to the next.

ISSN:0394-9370    

DOI:10.1080/08927014.2000.9522792

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Female southern elephant seals are expected to adopt behaviours that reduce the costs of male harassment. We studied the strategies and tactics of harassment reduction in two populations, at Punta Delgada (Valdés Peninsula, Argentina) and at Sea Lion Island (Falkland Islands) during five breeding seasons in all. Females synchronized their breeding activities to reduce harassment risk, and rarely bred alone to reduce the likelihood of encounters with subadult males. Females showed a clear preference for larger harems, that guaranteed a reduced harassment risk: movements between arrival on land and parturition were mostly from smaller to larger harems, and the likelihood of abandonment was lower for large harems. Females protested against approaching males in the vast majority of interactions, regardless of the social context and the status of the interacting male, but protest varied with female breeding status and male phenotype. Frequency of protest of individual females decreased linearly from the beginning of oestrus to departure to sea. Interactions with mature males were less protested. The frequency of protest linearly decreased with increase in age class, and mating attempts by males of higher status and dominance rank were less often protested. Most of this variation with male phenotype, however, was due to the higher probability of older and more dominant males to interact with oestrus females that had an intrinsicly lower tendency to protest. Protest variation in relation to male phenotype was more parsimoniously explained as a consequence of differential access of males to oestrus females rather than of female selectivity. Protests had a role in disruption of mating attempts, although the phenotype of interactors was more important: adult, large and dominant males disrupted interactions regardless of incitation by female protest.

ISSN:0394-9370    

DOI:10.1080/08927014.2000.9522793

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

During the breeding season female elephant seals spent most of their time on land inside harems. When they arrive on land before joining harems, and when they leave harems to return to sea, they are exposed to secondary males and may suffer intense harassment. Hence, arrival and departure present an ideal opportunity to test hypotheses concerning female tactics of harassment reduction. We studied harassment during arrival and departure in two southern elephant seal populations at Punta Delgada (Valdés Peninsula; DEL hereafter) and Sea Lion Island (Falkland Islands; SLI hereafter). Females were less likely to be intercepted by males during arrival than during departure. They also arrived mostly at high tide, thereby reducing the distance from water to the harems. Interception rate and harassment during departure were higher at DEL, where male density and the breeding sex ratio affected the likelihood of interception; on SLI, the socionomy had a small effect. Harassment was higher at low tide at DEL but not at SLI, because tide level variation was larger at DEL and this resulted in a larger variation in the distances of the harems from the water. Females departed more often than expected at high tide at DEL but not at SLI. In both populations females departed directly to sea, rarely stopping before reaching the water, and they never sought contact with males. Social distraction during departure significantly reduced the likelihood of interception. Departures were more frequent during periods of high social activity, and females departing just after other females were less prone to harassment. Accepting copulations with secondary males may reduce the dangerous effects of harassment: interactions occurring during departure were less frequently protested, but we found no indication that departing females were facilitating copulations in a special manner. Quantity and quality of protest during departures was similar to protest during the last days of residence of the females in the harem.

ISSN:0394-9370    

DOI:10.1080/08927014.2000.9522794

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Habitat use by mule deer was studied in the Mapimí Biosphere Reserve in the Chihuahuan Desert, Mexico. The deer population in this area is distributed among isolated hills and sierra. Because of their similar soil and vegetation characteristics, these hills are a homogeneous element of the landscape. This study was carried out within this element, in order to understand the habitat variables that are important for deer in the selection of habitat. Univariate as well as multivariate analytical methods were used in a complementary fashion to identify habitat variables associated with habitat selection during wet and dry seasons. The univariate method detected a relationship between habitat use and variation in slope (measurements of unevenness in terrain), in both seasons, it also detected a relationship between habitat use and the distance to water in the dry season. The multivariate method detected higher use of sites with greater unevenness in the terrain, higher shrub diversity, greater visibility and that were closer to water sources. Unevenness in terrain seems to be the most important factor influencing habitat selection by mule deer. This factor is limited to isolated hills and sierra in this part of the Chihuahuan Desert, so it is a spatially well defined resource. Such areas should be considered as a high-priority for the conservation of this species.

ISSN:0394-9370    

DOI:10.1080/08927014.2000.9522795

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The susceptibility of adult male and female dampwood termites (Zootermopsis angusticollis) to an infection carried by a mate was studied by exposing dealates to a 4 × 107or a 6 × 104spores/ml solution of the fungusMetarhizium anisopliae. Following exposure to spores, male and female dealates were paired randomly in four treatments: (1) male and female exposed to spores; (2) male exposed to spores/female exposed to a control solution lacking fungal spores; (3) male exposed to a control solution/female exposed to spores and (4) male and female exposed to a control solution. Males and females exposed to 4 × 107spores/ml acquired and transmitted the infection to their unexposed mate, and had significantly lower survival relative to controls. When males and females were exposed to 6 × 104spores/ml, however, there were no significant differences in survivorship among the four treatments. Therefore, at the lower pathogen load, dealates were able to control infection. To compare the susceptibility of exposed adults in the absence of social interactions, the survivorship of male and female dealates maintained in isolation following exposure to the lethal spore concentration (107spores/ml) was recorded. Male and female adults maintained in isolation had 1.5 times the hazard ratio of death of paired adults, suggesting that mate allogrooming and other social exchanges decreased disease susceptibility.

ISSN:0394-9370    

DOI:10.1080/08927014.2000.9522796

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor