The effect of season, sex and feeding style on home range area versus body mass scaling in temperate ruminants

Sex-specific estimates of the summer and winter home range area of 19 species of temperate ruminants were collated from the literature. It was predicted that there should be a shallower slope for the home range area against body mass relationship during winter than during summer, as large ruminants can meet more of their energy requirements from the fat reserves deposited during summer than small ruminants. Consequently, relatively large species do not need to range as widely during winter. There was a significant positive relationship between body mass and summer and winter home range area in both females and males. This relationship remained significant when analysed within feeding styles (browser, mixed feeder, grazer), except in mixed feeders in winter. As predicted, slope estimates were significantly lower during winter (b=0.59) than during summer (b=1.28), both before and after controlling for phylogeny. After controlling for phylogeny, browsers had a steeper slope (summer: b=1.48; winter: b=1.07) of the home range area against body mass relationship than did mixed feeders (summer: b=0.75; winter: b=-0.11) or grazers (summer: b=1.10; winter: b=0.34). There was no effect of sex after body mass was controlled for. The effect of season, sex and feeding style on the home range area versus body mass relationship in temperate ruminants is discussed.     

The functional relationship between feeding type and jaw and cranial morphology in ungulates

The relationship between jaw and skull morphology and feeding type (grazer, mixed feeder, browser, frugivorous, omnivorous) was analysed in 94 species of extant ungulates. A total of 21 morphological traits of the jaw and skull (17 and 4, respectively) were analysed using analysis of covariance, with body mass as covariate. To take into account the phylogenetic effect, simulations were generated under the Brownian motion model of character evolution. Analysis of covariance was applied to these simulations and the simulated F-ratios were used to assess the signification of the F-ratios for the real values of the traits. The feeding types had a weak effect on ungulate cranial and jaw morphology in comparison with the phylogenetic effect, since, before phylogeny correction, the analysis of covariance showed statistically significant differences associated with feeding type in 15 out of the 21 traits analysed. After controlling for phylogeny, only 2 significant traits remained, the length of the coronoid process and the occipital height. Omnivorous species had shorter coronoid processes than grazers or mixed feeders, and the occipital height was greater in the omnivorous species than in the grazers, mixed feeders or browsers. The coronoid process is involved in the generation of bite force, being the effective moment arm of the temporalis muscle, and occipital height is positively related to the force exerted by the temporalis muscle. This result matches the hypothesis that species with a toughness diet should show higher bite force (“toughness” describes the resistance of a material to being mechanically broken down). When the omnivorous species were excluded from the analysis, no differences in jaw and skull morphology were detected between the rest of the feeding types. Received: 1 September 1998 / Accepted: 2 November 1998     

Phylogenetic analysis of stomach adaptation in digestive strategies in African ruminants

The stomach morphology of 28 species of artiodactyls that differ in feeding style (browser, mixed feeder, grazer) was analysed using a multivariate approach and phylogenetic correction in order to test whether stomach morphology was correlated with feeding style when body mass was controlled for. A total of 25 morphological traits of the stomach were used in the analysis. After the effects of body mass and phylogeny on stomach morphology were taken into account, there was no significant grouping of species according to feeding style. When information about the feeding style of each species was included in the analysis, the set of morphological traits separated the mixed feeders from the other two feeding styles, but grazers and browsers had similar morphological features. Most of the variance in stomach morphology was explained by body mass and a lesser proportion by phylogeny. The main morphological features that have previously been proposed as being adaptations in grazing species, namely, lengthening of the retention time of ingesta to achieve an increase in their fibre digestion capability by means of a larger relative stomach capacity, a greater subdivision of chambers and smaller openings, are not supported by the findings of this study. Thus, there is no consistent evidence to support a significant adaptive effect of stomach morphology to different diets in the Artiodactyla.     

Intraspecific variation in Eucalyptus secondary metabolites determines food intake by folivorous marsupials

Traditional approaches to the question of the effects of plant secondary metabolites on the feeding choices of folivores of Eucalyptus have focused on the tree species level, although numerous field studies of foraging behaviour have identified selection at the level of the individual trees. Attempts to relate these decisions to deterrency resulting from secondary leaf chemistry have been inconclusive because assays used have focused on broad groups of compounds such as “total” phenolics. In this study we have conducted no-choice feeding trials with two arboreal mammalian folivores, the common ringtail possum (Pseudocheirus peregrinus) and the koala (Phascolarctos cinereus), to measure deterrency of individual trees of two species of Eucalyptus, E. ovata and E. viminalis. Average daily intakes of E. ovata foliage by common ringtail possums ranged from 2.5 to 50 g kg^−0.75 body mass. Koala intakes of foliage from the same individual trees ranged from 22.4 to 36.3 g kg^−0.75 body mass. When fed foliage from different individual E. viminalis trees, common ringtail possums ate between 1.26 and 6.28 g kg^−0.75 body mass while koalas ate from 14.3 to 45.9 g kg^−0.75 body mass. Correlative analyses showed no relationships between feeding and several measures of nutritional quality, nor with total phenolics or condensed tannins. They did, however, identify two groups of plant secondary metabolites that may cause deterrency: terpenes, and a defined group of phenolic compounds, the diformylphloroglucinols (DFPs). Further bioassay experiments with common ringtail possums showed that only the DFPs could cause the effects seen with the foliage experiments at concentrations similar to those found in the leaves. We argue that, when in sufficiently high concentrations, DFPs determine the level of food intake by these animals irrespective of other questions of nutritional quality of the leaves. Received: 20 October 1997 / Accepted: 23 March 1998     

Relationships between oral morphology and feeding style in the Ungulata: a phylogenetically controlled evaluation

In ungulates it is argued that specialization in the consumption of a particular type of food (feeding style) is reflected in morphological adaptations of the organs involved in the selection, processing and digestion of food. We analysed the differences in size and morphology of some oral traits that have been functionally related to food-selection ability (muzzle width, incisor-arcade shape, incisor shape), prehension of food (incisor protrusion), food comminution (molar occlusal surface area, hypsodonty (high-crowned molars)) and intake rate (incisor breadth) between ungulate species with different feeding styles (browser, mixed feeder, grazer). Grazers were characterized by large-body-size species. After controlling only for body mass, we found that grazers had wider muzzles and incisors, more-protruding incisors and more-bulky and higher-crowned molars than did mixed feeders and browsers. When the analyses took into account both body mass and phylogeny, only body mass and two out of the three hypsodonty indexes used remained significantly different between feeding styles. Browsers were smaller, on average, than mixed feeders and grazers, whilst grazers and mixed feeders did not differ in size. Also, browsers had shorter and less-bulky molars than did mixed feeders and grazers; the latter two feeding styles did not differ from each other in any of the hypsodonty indexes. We conclude that the adaptation to different dietary types in most of the oral traits studied is subsumed by the effects of body mass and the sharing of common ancestors. We hypothesize that differences in the ability to exploit different food resources primarily result from differences in body mass between species, and also discuss why hypsodonty characterizes feeding styles.     

Gregariousness increases brain size in ungulates

The brain’s main function is to organise the physiological and behavioural responses to environmental and social challenges in order to keep the organism alive. Here, we studied the effects that gregariousness (as a measurement of sociality), dietary habits, gestation length and sex have on brain size of extant ungulates. The analysis controlled for the effects of phylogeny and for random variability implicit in the data set. We tested the following groups of hypotheses: (1) Social brain hypothesis—gregarious species are more likely to have larger brains than non-gregarious species because the former are subjected to demanding and complex social interactions; (2) Ecological hypothesis—dietary habits impose challenging cognitive tasks associated with finding and manipulating food (foraging strategy); (3) Developmental hypotheses (a) energy strategy: selection for larger brains operates, primarily, on maternal metabolic turnover (i.e. gestation length) in relation to food quality because the majority of the brain’s growth takes place in utero, and finally (b) sex hypothesis: females are expected to have larger brains than males, relative to body size, because of the differential growth rates of the soma and brain between the sexes. We found that, after adjusting for body mass, gregariousness and gestation length explained most of the variation in brain mass across the ungulate species studied. Larger species had larger brains; gregarious species and those with longer gestation lengths, relative to body mass, had larger brains than non-gregarious species and those with shorter gestation lengths. The effect of diet was negligible and subrogated by gestation length, and sex had no significant effect on brain size. The ultimate cause that could have triggered the co-evolution between gestation length and brain size remains unclear.     

The role of an epipharyngeal sensillum in the perception of feeding deterrents by Leptinotarsa decemlineata larvae

An epipharyngeal taste sensillum in Leptinotarsa decemlineata larvae was studied. Electron microscopy showed that the sensillum is innervated by five neurons. Electrophysiological experiments showed that one of these cells responds to water, a second to sucrose and a third to two feeding deterrents that were also effective in a behavioural test. Receptor cells sensitive to feeding deterrents were not previously reported for L.␣decemlineata larvae or adults. The response of the sucrose-sensitive cell was strongly inhibited by one of the two feeding deterrents and only slightly by the other feeding deterrent. The relationship between the behavioural and electrophysiological results is discussed in order to elucidate the neural code of feeding deterrents in L. decemlineata larvae. We conclude that probably both the response of the deterrent cell and peripheral interactions exerted by feeding deterrents on the sucrose-sensitive cell determine the potency of feeding deterrents. The present results provide a physiological basis for the hypothesis that the presence or absence of feeding deterrents in potential food plants is a decisive cue in food plant selection by L. decemlineata larvae. Accepted: 25 March 1998     

Refuge use by fish as a function of body weight changes

Refuge use provides a good model for the study of trade-offs between the benefits of predator avoidance and the costs of lost feeding opportunities. We manipulated the latter costs by subjecting similar-sized three-spine sticklebacks to 2 days of food deprivation followed by a 2-day re-feeding period and recorded associated changes in body weight and refuge use. Food deprivation resulted in a decrease and re-feeding in an increase in the duration of refuge use by fish. Emergence times of fish from the refuge were extremely variable (with a ratio of 1:127 between the shortest and the longest ones) but individual ranks were highly consistent between different days of testing, suggesting that emergence times were individually characteristic. Percentage weight change of fish in response to the experimental treatments also showed a high level of inter-individual variation ranging from 0–17%. A significant positive correlation was found between the percentage weight lost and the percentage decrease in emergence time from a refuge after food deprivation and similarly between the percentage weight gained and the percentage increase in refuge use after re-feeding. The relationship between energy turnover and behavioural strategies is discussed. Received: 13 December 1998 / Received in revised form: 2 May 1999 / Accepted: 7 June 1999     

Pedal Claw Curvature in Birds,Lizards and Mesozoic Dinosaurs – Complicated Categories and Compensating for Mass-Specific and Phylogenetic Control

Pedal claw geometry can be used to predict behaviour in extant tetrapods and has frequently been used as an indicator of lifestyle and ecology in Mesozoic birds and other fossil reptiles, sometimes without acknowledgement of the caveat that data from other aspects of morphology and proportions also need to be considered. Variation in styles of measurement (both inner and outer claw curvature angles) has made it difficult to compare results across studies, as have over-simplified ecological categories. We sought to increase sample size in a new analysis devised to test claw geometry against ecological niche. We found that taxa from different behavioural categories overlapped extensively in claw geometry. Whilst most taxa plotted as predicted, some fossil taxa were recovered in unexpected positions. Inner and outer claw curvatures were statistically correlated, and both correlated with relative claw robusticity (mid-point claw height). We corrected for mass and phylogeny, as both likely influence claw morphology. We conclude that there is no strong mass-specific effect on claw curvature; furthermore, correlations between claw geometry and behaviour are consistent across disparate clades. By using independent contrasts to correct for phylogeny, we found little significant relationship between claw geometry and behaviour. ‘Ground-dweller’ claws are less curved and relatively dorsoventrally deep relative to those of other behavioural categories; beyond this it is difficult to assign an explicit category to a claw based purely on geometry.     

Bioenergetic Constraints on Primate Abundance

Explaining variation in primate population densities is central to understanding primate ecology, evolution, and conservation. Yet no researchers to date have successfully explained variation in primate population density across dietary class and phylogeny. Most previous work has focused on measures of food availability, as access to food energy likely constrains the number of individuals supported in a given area. However, energy output may provide a measure of energy constraints on population density that does not require detailed data on food availability for a given taxon. Across mammals, many studies have shown that population densities generally scale with body mass^−0.75. Because individual energy expenditures scale with body mass^0.75, population energy use (the product of population density and individual energy use) does not change with body mass, which suggests the existence of energy constraints on population density across body sizes, i.e., taxa are limited to a given amount of energy use, constraining larger taxa to lower densities. We examined population energy use and individual energy expenditure in primates and tested this energy equivalence across body mass. We also used a residual analysis to remove the effects of body mass on primate population densities and energy expenditures using basal metabolic rates (BMR; kcal/d) as a proxy for total daily energy expenditure. After taking into account phylogeny, population energy use did not significantly correlate with body mass. Larger primates, which use more energy per day, live at lower population densities than smaller primates. In addition, we found a significant negative correlation between residuals of BMR from body mass and residuals of population density from body mass after taking phylogeny into account. Thus, energy costs constrain population density across a diverse sample of primates at a given body mass, and primate species that have relatively low BMRs exist at relatively high densities. A better understanding of the determinants of primate energy costs across geography and phylogeny will ultimately help us explain and predict primate population densities.     

Body condition of shorebirds upon arrival at their Siberian breeding grounds

Arctic breeding shorebirds carry substantial body stores on their long-distance migrations from their non-breeding grounds. Upon arrival at the breeding area the remains of these stores can be used for egg formation, insurance against poor feeding conditions or rebuilding organs. We quantified body condition (body mass, total body water, lean body mass and fat mass estimated using the deuterium dilution method) in seven shorebird species caught upon arrival in the Siberian Arctic. Arrival condition was compared with incubation condition in a subset of species. After correction for structural size, body mass was significantly lower at arrival than during incubation in most of the species (but 3–18% above lean mass). Fat index (fat mass/lean mass) varied between 5.1 and 13.2%. Fat stores were estimated to enable survival for 0.6 days for the smallest and 2.5 days for the largest species. We discuss possible functions of arrival stores: insurance, egg-formation or rebuilding organs. G. H. Visser: Deceased.     

Development of size structure in tiger salamanders: the role of intraspecific interference

Cannibalism affects patterns of density-dependent mortality and may regulate population size. In many cases, rates of cannibalism depend on size structure, the frequency distribution of body sizes in the population, because cannibals can often only capture and consume smaller individuals. Size differences within single-age groups can be caused by a variety of factors. In this research we tested the hypothesis that size variation among larval tiger salamanders is due, in part, to interference interactions among individuals of different sizes. We found that size variation was greater when we raised larvae in groups rather than in isolation. This increase in size variation was due more to a relative deceleration of growth among smaller individuals rather than acceleration among larger individuals. We also found that smaller larvae had lower feeding rates than larger larvae when in groups, but not when isolated. Including spatial structure to limit physical interactions did not affect the size specificity of feeding rate, although it reduced feeding rates overall. We argue that these results are consistent with the hypothesis that larger larvae interfere, probably indirectly, with the feeding behavior of small individuals and this contributes to increases in size variation over time. We hypothesize that this indirect interference is caused by a behavioral response of smaller larvae to the risk of predation (cannibalism) by larger individuals. Received: 18 May 1998 / Accepted: 29 April 1999     

Seed mass and germination in an alpine meadow on the eastern Tsinghai–Tibet plateau

In this study, we built up a database of 570 species from an alpine meadow on the eastern Tsinghai–Tibet plateau. We examined the correlation of seed mass and germination with phylogeny, habitat and altitude, and the relationship between seed mass and germination. We found that: habitats had no significant effects on seed mass and germinability, which was in accord with the former studies; there was a significant negative correlation between seed mass and altitude, as well as between germinability and altitude, which was opposite to most of the former studies; there was a significant negative correlation between seed mass and germinability, which was in contrast with other studies that have found a positive relationship, and seed mass could explain 24.1% of total variation in germinability; in GLM, family and genus accounted for 43.9% and 83.9% of total variation in seed mass, and 34.1% and 65.4% in germinability, respectively, thus, it was evident that seed mass and germinability were strongly related to phylogeny. We considered that seed mass and germination might be the result of both selective pressures over long-term ecological time and the constraints over long-standing evolutionary history of the taxonomic membership. We suggest that correlates of ecology and phylogeny should be taken into account in comparative studies on seed mass and germination among species.     

A Phylogenetic Study of Late Growth Events in a Mammalian Evolutionary Radiation—The Cranial Sutures of Terrestrial Artiodactyl Mammals

We recorded the relative timing of fusion of 29 ectocranial sutures in 480 skulls belonging to 35 extant and four fossil species from all major clades of terrestrial artiodactyls. The resulting data were studied in a phylogenetic context, using mapping of event-pairing of suture fusion events and Parsimov. As phylogenetic framework we generated a compound phylogeny from several previously published analyses. Overall suture closure per species ranged from five to all 29 sutures in Hexaprotodon. All living non-ruminants (suids, camelids, and hippopotamids) fuse more than 50% of the studied sutures (most over 75%), whereas in almost all ruminants less than 50% of the sutures fuse completely. Phylogenetic regression found a significant correlation between suture closure and body mass. In all species we observed an early fusion of the sutures surrounding the foramen magnum (Exoccipital-Supraoccipital, Exoccipital-Basioccipital), a consistent scheme also among other mammals. Scaling the number of changes to the number of sutures in each of the usually recognized skull modules reveals relatively equal numbers of changes in the cranial vault, the zygomatic-sphenoid region, the orbit, and the anterior oral-nasal region. Only the basicranium shows a much smaller number in terms of absolute and relative amount of suture fusion change. Some species show a unique pattern of suture fusion, such as the early fusion of many sutures in the palatal region in Pecari or that of premaxillary sutures in †Cainotherium, perhaps related to feeding mode. A strategy to strengthen the skull by obliterating the sutures could explain the pattern of increased sutural fusion in ruminant species with large cranial appendages.     

Thermoregulatory differences between phenotypes in the speckled wood butterfly: hot perchers and cold patrollers?

Males of the speckled wood butterfly Pararge aegeria L. (Satyrinae), actively search for females (“patrolling”) or wait for them at particular places (“perching”). Darker males are more likely to patrol than pale ones, which are mainly territorial perchers. We studied whether this morphological variation relates to thermoregulatory differences. The relationship between thoracic temperature and ambient temperature differed between the colour types under natural conditions: darker males had on average lower body temperatures than paler males. Different activities (e.g. resting, flying) and behavioural strategies (perching or patrolling) were associated with differences in thoracic temperature: patrolling males which mainly engaged in long flights and periods of basking afterwards, had lower thoracic temperatures than perching males which engaged in very short flights, fights and basking. When resting for a while thoracic temperatures did not differ between males practising different strategies. Under laboratory conditions, darker males heated up faster than pale males but there was no difference in the thoracic temperature at which they started to fly. These results indicate that thermal requirements (or general conditions) differ between the behavioural strategies, and that behavioural differences between phenotypes (colour types) relate to differences in thermal ecology. This supports the idea that darker males are better adapted to patrolling. There is no evidence that one mate-locating strategy is always superior to the other, which coincides with the observation that both strategies co-exist. More generally, this study shows that relatively small differences in colour can have a considerable effect on thermoregulation and hence on the behavioural strategies a heliothermic insect will adopt. Received: 15 August 1997 / Accepted: 15 December 1997     

Coevolution of the mammalian chemokines and their receptors

 A phylogeny of mammalian chemokines revealed two major clusters, corresponding to the CC and CXC chemokines; the C chemokines appeared to be more closely related to the former. In a phylogeny of chemokine receptors, there were also two major clusters: one containing CC chemokine receptors plus other receptors of unknown function and another containing CXC receptors and other receptors of unknown function. However, within the CC receptors, there was not a close correspondence between the phylogenies of chemokines and their receptors. The CC chemokines contained two major subfamilies: (1) the MIP subfamily (including MIP-1α, MIP-1β, and RANTES); and (2) the MCP subfamily (including MCP-1,-2,-3, and -4 and eotaxin). Receptors having preferred ligands in the MCP subfamily did not constitute a monophyletic group but rather evolved twice independently. Reconstruction of ancestral amino acid sequences suggested that these two groups of MCP receptors did not convergently evolve any amino acid residues; rather, they convergently lost sequence features found in the third and fourth extracellular domains of known receptors for MIP-subfamily chemokines. Received: 1 May 1998 / Revised: 3 July 1998     

The metabolic rates associated with resting, and with the performance of agonistic, submissive and digging behaviours in the cichlid fish Neolamprologus pulcher (Pisces: Cichlidae)

We measured the metabolic rates as a direct estimate of energy expenditure of individual Neolamprologus pulcher, a cooperatively breeding cichlid fish, when resting and when performing agonistic, submissive or digging behaviours in a respirometer. Standard and routine metabolic rates increased linearly with body mass (range 0.9–8.4 g) when plotted on a doubly logarithmic scale (linear regression equations: standard metabolic rate: log individual oxygen consumption rate = 0.65 + 0.86 log body mass; routine metabolic rate: log individual oxygen consumption rate = 0.75 + 0.86 log body mass). Routine metabolic rates were, on average, 30% higher than standard metabolic rates. Submissive and agonistic behaviours raised routine metabolic rates by factors of 3.3 and 3.9, respectively. Digging resulted in a 6.1-fold increase of routine metabolic rates. Differences in metabolic rates between active and resting rates were statistically significant. However, those between the three behaviours were not. Mean opercular beat frequencies correlated significantly with routine metabolic rates and with metabolic rates when performing specific behaviours, which offers methodological prospects for field measurements. In N. pulcher, the high energy expenditure for submissive behaviour may indicate that this is a reliable signal. The considerable energy expenditure involved in territory defence suggests that these costs should be considered in addition to risk in cost-benefit analyses. This is the first study in which the energy expenditures of specific social and territory maintenance behaviours of individual fish were measured directly by respirometry and within the usual social setting of the fish. Accepted: 20 February 1998     

Prevalence and intensity of excretion of coccidial oocysts in migrating passerines on Helgoland

Prevalence and intensity of excretion of coccidial oocysts in actively migrating passerines (Turdus philomelos, Fringilla coelebs, Sylvia borin, Phoenicurus phoenicurus) were assessed in spring and autumn 2001 during stopovers on Helgoland. All examined species showed low prevalences of oocysts in spring (28–33%) and high prevalences in autumn migration (66–92%). In autumn, there are significant species-specific differences in prevalence and, partially, in intensity of excretion. Ground-feeding Chaffinches most commonly and most intensively shed oocysts (maximal 2,7×10⁶ oocysts per g fresh faeces) indicating that feeding style may influence the parasite load. No significant correlation between parasite load, age, and body condition (fat depots, breast muscle shape, body mass) was found. The connection between feeding style, age, migration, immunocompetence, and survival of passerine hosts on one hand and the particularities of coccidial pathogenicity on the other are discussed.     

Experimental evidence of cost of lactation in a low risk environment for a long-lived mammal

In a previous experiment we have documented that organisms adopt a risk-sensitive reproductive allocation when summer reproductive investment competes with survival in the coming winter ( Bårdsen et al. 2008 ). This tradeoff is present through autumn female body mass, which acts as an insurance against unpredictable winter environmental conditions. We tested this hypothesis experimentally on female reindeer experiencing stable and benign winter feeding conditions. Additional supplementary feeding and removal of newborns represented two sets of experimental manipulations. Females in the supplementary feeding group increased more in winter body mass relative to control females. This manipulation, however, did not have any effect on summer body mass development for neither females nor offspring, but we found a positive effect of feeding on offspring birth mass for smaller females. In contrast, offspring removal did have a positive effect on summer body mass development as females in this group were larger in the autumn relative to control females. In essence, we documented two immediate effects as: (1) supplementary feeding did have a positive effect on spring body mass for smaller females; and (2) offspring removal did increase the female summer somatic growth as this had a positive effect on female autumn body mass. Additionally, we tested for lagged effects, but we could not document any biologically significant effects of neither manipulation in the coming spring. The fact that we only found rather weak effects of both manipulations was as expected for risk sensitive individuals experiencing benign environmental conditions over many years.