Search results for "Animal Ecology"
showing 10 items of 120 documents
Testing the assumptions of conditional handicap theory: costs and condition dependence of a sexually selected trait
2000
Conditional handicap models of sexual selection predict that sexual traits are reliable signals of male quality because they are (a) condition dependent and (b) costly to produce or maintain. In this study, my objective was to experimentally investigate whether the drumming of male Hygrolycosa rubrofasciata wolf spiders is a condition-dependent costly trait. Males court females by drumming dry leaves with their abdomen and females preferentially mate with males drumming at higher rates. I manipulated male phenotypic condition and drumming rate simultaneously by keeping males on three different food rations and either introducing or not introducing them to a female. Food ration treatment aff…
Not everything is everywhere: the distance decay of similarity in a marine host-parasite system
2009
Aim We test the similarity–distance decay hypothesis on a marine host–parasite system, inferring the relationships from abundance data gathered at the lowest scale of parasite community organization (i.e. that of the individual host). Location Twenty-two seasonal samples of the bogue Boops boops (Teleostei: Sparidae) were collected at seven localities along a coastal positional gradient from the northern North-East Atlantic to the northern Mediterranean coast of Spain. Methods We used our own, taxonomically consistent, data on parasite communities. The variations in parasite composition and structure with geographical and regional distance were examined at two spatial scales, namely loca…
Black Grouse leks on ice: Female mate sampling by incitation of male competition?
1995
Male-male competition is assumed to limit female choice of mates, but it may also help females to choose the most vigorous males. We studied the mate sampling behaviour of female black grouse (Tetrao tetrix) at spatially unstable leks on ice-covered lakes. In the absence of territories and site-dependence in outcomes of fights, the male dominance hierarchy is very evident on ice. When being courted by dominant males, females frequently tried to approach other males. This was frequently prevented because (1) the courting male and the approached male were involved in physical fight, or (2) the dominant male followed the female and the approached male escaped and avoided contact with him. Thes…
Dietary divergence in space and time – Lessons from the dwarf-goat Myotragus balearicus (Pleisto-Holocene, Mallorca, Spain)
2013
8 pages; International audience; Newly colonised, isolated habitats, like islands, provide diverse niches to be filled and are prone to facilitate ecological separation which might lead to an adaptive radiation. Examples of such radiations can be found in the Mediterranean for the genera Candiacervus (Crete), Nesogoral (Sardinia) and Hoplitomeryx (Gargano). A different strategy to cope with limited resources on islands is generalism. We test whether populations of the endemic bovid Myotragus balearicus from two sites and Pleistocene as well as Holocene levels on Mallorca island displays ecological separation indicated by diet, or whether the species shifted its dietary trait towards general…
Population changes in Czech passerines are predicted by their life-history and ecological traits
2010
A species’ susceptibility to environmental change might be predicted by its ecological and life-history traits. However, the effects of such traits on long-term bird population trends have not yet been assessed using a comprehensive set of explanatory variables. Moreover, the extent to which phylogeny affects patterns in the interspecific variability of population changes is unclear. Our study focuses on the interspecific variability in long-term population trends and annual population fluctuations of 68 passerine species in the Czech Republic, assessing the effects of eight life-history and five ecological traits. Ordination of life-history traits of 68 species revealed a life-history grad…
The desert at Zait Bay, Egypt: a bird migration bottleneck of global importance
2009
The study area at Zait Bay, Egypt (c. 700 km2) is situated in the middle of the West Asian-East African migration flyway used by very large numbers of soaring migrants. At this site the corridor narrows into a bottleneck. There exist only very few bottlenecks of this magnitude in the world. Observations were performed at all hours between sunrise and sunset at 26 observation sites, situated 5 km apart. The northern part of the area under investigation (19 observation sites) was situated within the Gebel El Zeit IBA (criteria A1 and A4iv), while the southernmost part (8 observation sites) was outside. The overall evaluation has shown that 179,681 soaring birds including 122,454 storks and 36…
Joint brood guarding in parent bugs — an experiment on defence against predation
1995
Females of Elasmucha grisea defend their eggs and small nymphs against invertebrate predators. Females sometimes guard their clutches side by side on the same birch leaf. We studied benefits of this joint guarding both in the field and in the laboratory. We found that adjacent females had significantly larger clutches than solitary females. In the laboratory, we studied the effectiveness of joint versus single defence against ant (Formica uralensis) predators. We established female pairs from initially singly guarding females by cutting off pieces of leaves with egg clutches and pasting them beside another female guarding her clutch. In the control group the females with their clutches were…
Sexual signalling and viability in a wolf spider ( Hygrolycosa rubrofasciata ): measurements under laboratory and field conditions
1999
This study examined the crucial prediction of the conditional-handicap theory, the relationship between male sexual trait size and male viability, in the wolf spider Hygrolycosa rubrofasciata. In this species, males court females by drumming dry leaves with their abdomen, and males with the highest drumming rate enjoy highest mating success. We determined male drumming rate, body mass, and mobility, which reflects mate-searching activity, in relation to male survival. Because it is often difficult to know how results obtained from laboratory studies reflect the natural world, particularly when the measured variable is survival, we repeated our study in both laboratory and field conditions. …
Influence of temperature on the oviposition rate and longevity ofOpius concolor siculus [Hymenoptera: Braconidae]
1974
The author has studied the influence of different temperatures (22°, 24°, 26°, 28°C) on oviposition and longevity ofOpius concolor siculusMon., studying separately 13 couples at 22°, 15 at 24°, 100 at 26° and 11 at 28°C.
Effects of male removal on female foraging behavior in the Eurasian treecreeper
1997
In old, spruce-dominated forests of central Finland, Eurasian treecreepers Certhia familiaris divide their territories spatially during the breeding season. Females forage primarily on the upper parts of the tree trunks, while males use the lower parts of the tree trunks. In this study we removed males from eight territories in the early nestling period to see if the mate's absence would change the foraging patterns of the resident female. Widowed females foraged at lower heights, thus behaving more like paired males. These females also spent less time on each tree and on each foraging bout than did paired females. We conclude that male removal facilitated the change in a female's foraging …