The primary structure of the hemoglobin of the Indian false vampire (Megaderma lyra, Microchiroptera)

The hemoglobin of the Indian false vampire Megaderma lyra contains only one component. In this paper, we are presenting its primary structure. The globin chains were separated by high-performance liquid chromatography and the sequences determined by automatic liquid and gas phase Edman degradation of the chains and their tryptic peptides, as well as of the prolyl-peptides obtained by acid hydrolysis of the Asp-Pro bond in the alpha- and beta-chains. The alpha-chains show 23 and the beta-chains 20 exchanges compared with the human alpha- and beta-chains, respectively. In the alpha-chains, three exchanges involved alpha 1/beta 1 contacts. In the beta-chains one heme-and three alpha 1/beta 1 contacts are exchanged. The functional and systematic aspects of these replacements are discussed.     

Siblicide in the spotted hyena: analysis with ultrasonic examination of wild and captive individuals

Integrated field and laboratory studies of long-lived, large-bodiedmammals are rare but offer unique opportunities to elucidatethe behavioral ecology of these animals. Here, we used thisapproach to examine whether siblicide in spotted hyenas (Crocutacrocuta) is obligate or facultative. First, we tested predictionsof obligate and facultative hypotheses by using ultrasonographyto compare litter size before and after parturition and identifypotential causes of litter reduction. Second, we compared littersize and composition between wild and captive hyenas to assessvariation in offspring sex ratios. Third, we used demographicdata to compare survivorship among litters of various sizesand compositions. Fourth, we compared sex ratios within twinlitters born in the wild under conditions of high populationdensity and intense feeding competition with those born whenpopulation density and intensity of feeding competition werereduced. Our data were inconsistent with the obligate siblicidehypothesis. Litter reduction occurred during roughly one-thirdof pregnancies in both wild and captive hyenas, and all suchreductions among captives were due to fetal resorptions or stillbirths.Litter sizes and compositions differed little between wild andcaptive hyenas. However, sex ratios in twin litters varied inthe wild with intensity of feeding competition. In conjunctionwith captive data, long-term study of a wild hyena populationunder varying environmental conditions suggests facultativesiblicide is most likely to occur when feeding competition ismost intense, thus offering an ecological explanation for earlierconflicting reports on siblicide in this species.     

Do plant parts compete for resources? An evolutionary viewpoint

Simultaneously growing sinks are thought to compete for plant resources. Negative correlations, for example between grain number and stem mass in cereals, indeed resemble competition; but is the notion of intra-plant competition evolutionarily justified? Here we review intra-plant competition in light of two aspects of evolutionary biology: (a) major transitions that led to the reorganization of evolutionary individuals (e.g. isolated DNA molecules and independent cells) into new units of adaptation (e.g. chromosomes and multicellular organisms) with associated constraints to intra-individual conflict; and (b) genomic conflicts within individual plants with implications for resource allocation. Against this background, we look at apparent competition among genetically identical plant parts, and conclude that plants might use competition-like mechanisms to allocate resources, but only to the extent that these proximate mechanisms enhance overall plant fitness. In dealing with apparent competition among genetically different plant structures, we emphasize developing seeds attached to the same maternal plant, and the determination of yield components in annual crops. We propose that competition-like mechanisms among genetically different plant parts have been strongly shaped by the evolution of genomic conflict between parent and offspring, between female and male parents, and among siblings. By defining the number and potential size of grain simultaneously and before fertilization, a strong maternal control of resource allocation is exerted that favours uniform offspring size and partially counteracts genomic conflict.     

Aggressive monopolization of mobile carers by young of a cooperative breeder

Competition between young of the same brood or litter is of particular interest in the fields of behavioural and evolutionary ecology, because the competing individuals are likely to be closely related, where evolutionary theory predicts a greater degree of cooperation. Studies of cooperative breeding species typically concentrate on who contributes care to rearing young, and assume a passive role of the young. Relatively, little attention has been devoted to considering how intralitter competition between young affects the distribution of care in cooperative breeders. In banded mongoose (Mungos mungo) groups, the majority of pups each form a stable exclusive one-to-one association with an adult group member (its 'escort') that is its principal care provider. This paper presents experimental evidence that each pup aggressively defends access to its escort, preventing other pups approaching, and therefore monopolizes the care provided by its escort. Each pup travels with the group and follows its escort, around which its exclusion zone is fixed: a form of mobile territoriality. This represents a novel system of care of young in a mammal species, but has general implications for the study of the distribution of care of young, particularly in cooperative breeding species. Parents and helpers may provide biased care to young, not due to preference but due to the competitive actions of the young within the brood or litter.     

Effects of short-term hunger and competitive asymmetry on facultative aggression in nestling black guillemots Cepphus grylle

Siblings in a diversity of species are facultatively aggressive,yet the proximate control of the aggressive response and theecological conditions selecting for such systems are poorlyunderstood. In this study, we investigated the effects of foodamount (food amount hypothesis) and competitive asymmetry onsibling aggression in black guillemot broods. Parental provisioningrates were experimentally manipulated in broods comprisinga range of hatching intervals over a 12-h period. Aggressionbecame evident only after parental provisioning rates wereexperimentally reduced. When parental provisioning resumed,adults did not increase their feeding rate to compensate forthe induced food deficit, and the result of sibling rivalrywas a change in the allocation of parental deliveries from oneof equality to one in favor of the dominant chick. Food-deprivedchicks from synchronous broods were more aggressive than thosefrom asynchronous broods, suggesting that one benefit of hatchingasynchrony in the black guillemot is to establish an efficientcompetitive hierarchy among siblings which minimizes the needfor costly aggressive interactions. On the following day, siblingaggression ceased, and chicks regained an equal share of parentalfeeds. Our results provide the first evidence that short-termfood shortage per se acts as an initial trigger for aggressionand also show that the aggressive response is complicated byfactors associated with hatching and laying order.     

Energetic cost of hovering flight in nectar-feeding bats (Phyllostomidae: Glossophaginae) and its scaling in moths, birds and bats

Three groups of specialist nectar-feeders covering a continuous size range from insects, birds and bats have evolved the ability for hovering flight. Among birds and bats these groups generally comprise small species, suggesting a relationship between hovering ability and size. In this study we established the scaling relationship of hovering power with body mass for nectar-feeding glossophagine bats (Phyllostomidae). Employing both standard and fast-response respirometry, we determined rates of gas exchange in Hylonycteris underwoodi (7 g) and Choeronycteris mexicana (13–18 g) during hover-feeding flights at an artificial flower that served as a respirometric mask to estimate metabolic power input. The O₂ uptake rate (V˙ _o2) in ml g⁻¹ h⁻¹ (and derived power input) was 27.3 (1.12 W or 160 W kg⁻¹) in 7-g Hylonycteris and 27.3 (2.63 W or 160 W kg⁻¹) in 16.5-g Choeronycteris and thus consistent with measurements in 11.9-g Glossophagasoricina (158 W kg⁻¹, Winter 1998). V˙ _o2 at the onset of hovering was also used to estimate power during forward flight, because after a transition from level forward to hovering flight gas exchange rates initially still reflect forward flight rates. V˙ _o2 during short hovering events (<1.5 s) was 19.0 ml g⁻¹ h⁻¹ (1.8 W) in 16-g Choeronycteris, which was not significantly different from a previous, indirect estimate of the cost of level forward flight (2.1 W, Winter and von Helversen 1998). Our estimates suggest that power input during hovering flight P _h (W) increased with body mass M (kg) within 13–18-g Choeronycteris (n = 4) as P _h  = 3544 (±2057 SE) M ^{1.76 (±0.21 SE)} and between different glossophagine bat species (n = 3) as P _h  = 128 (±2.4 SE) M ^{0.95 (±0.034 SE)}. The slopes of three scaling functions for flight power (hovering, level forward flight at intermediate speed and submaximal flight power) indicate that: 1. The relationship between flight power to flight speed may change with body mass in the 6–30-g bats from a J- towards a U-shaped curve. 2. A metabolic constraint (hovering flight power equal maximal flight power) may influence the upper size limit of 30–35 g for this group of flower specialists. Mass-specific power input (W kg⁻¹) during hovering flight appeared constant with regard to body size (for the mass ranges considered), but differed significantly (P < 0.001) between groups. Group means were 393 W kg⁻¹ (sphingid moths), 261 W kg⁻¹ (hummingbirds) and 159 W kg⁻¹ (glossophagine bats). Thus, glossophagine bats expend the least metabolic power per unit of body mass supported during hovering flight. At a metabolic power input of 1.1 W a glossophagine bat can generate the lift forces necessary for balancing 7 g against gravitation, whereas a hummingbird can support 4 g and a sphingid moth only 3 g of body mass with the same amount of metabolic energy. These differences in power input were not fully explained by differences in induced power output estimated from Rankine-Froude momentum-jet theory. Accepted: 10 November 1998     

Begging at high level simultaneously impairs growth and immune response in southern shrike (Lanius meridionalis) nestlings

Theoretical models suggest that begging should be costly in order to be evolutionarily stable. However, evidence for such a cost is contradictory (e.g. for growth costs) or scant (e.g. for immunological costs). Here, we experimentally test the existence of both costs in southern shrike (Lanius meridionalis) nestlings. Nestlings were paired by nest of origin and similar body mass. In each pair, a nestling was forced to beg for about 30 s h(-1) , whereas the other begged for only 2 s, both nestlings receiving the same quantity of food. At the same time, the nestling response to an antigen (phytohaemagglutinin) was measured. Nestlings forced to beg for longer showed a reduction in growth rate and in immunocompetence when compared to control chicks. The two costs occurred independently of each other and were negatively correlated to time begging. These results strongly support models of honest signalling as well as scramble competition, which predict that begging should be costly in order to be evolutionarily stable.     

Energy, water balance and the roost microenvironment in three Australian cave-dwelling bats (Microchiroptera)

The ghost bat, Macroderma gigas, and the orange leaf-nosed bat, Rhinonycteris aurantius, occupy similar ranges across northern Australia and are often found in the same roost caves. Both species are considered rare and vulnerable to further population decline. A third small species, the large bent-wing bat, Miniopterus schreibersii, has a similar body mass to R. aurantius, but has one of the largest ranges of any Australian mammal. In the present study we examine the effect and sensitivity of the animals' roosting microclimates on their energy and water balance. M. schreibersii exhibits a basal metabolic rate about 40% greater than other bats of similar body mass, whereas the other two species are close to predicted levels. R. aurantius shows a decrease in body temperatures below thermoneutrality. R. aurantius has levels of pulmocutaneous water loss among the highest seen for a mammal, and calculations based on nasal tip temperatures suggest that most of this loss is across the skin. Calculated ambient temperatures at which metabolic water production is equal to pulmocutaneous water loss in dry air are −14.7 °C for R. aurantius, 9.8 °C for M. schreibersii and −0.3 °C for M. gigas. Exposing the animals to relative humidities of between 80% and 90% shifted these calculated temperatures to 5.6 °C, 25.2 °C, and 2.9 °C, respectively. For each species the ratio of metabolic water production to evaporative water loss has been treated as a joint function of humidity and ambient temperature. The resulting surface plot shows that under known roosting conditions in caves R. aurantius and M. schreibersii remain in positive water balance, whereas M. gigas does not. Accepted: 20 May 2000     

Mineral nutrient stoichiometric variability in Hedera helix (Araliaceae) seeds

Background and Aims

The analysis of variability in mineral allocation to seeds has rarely been considered in relation to allometric patterns and deviations from the allometric trajectory. Here, I examine the scaling of carbon (C), nitrogen (N), phosphorus (P) and sulfur (S) with seed mass in field-collected seeds of Hedera helix, taking into account that brood size might influence the allocation patterns.

Methods

C, N and S contents of 56 individual seeds of different sizes were analysed by combustion using a standard automated CNHS procedure. P content was determined for 200 individual seeds using spectrophotometry after acid digestion of ashed samples. This sample included seeds from different brood sizes.

Key Results

C and N content both varied isometrically with seed mass and this variable explained most of the variation in their content in seeds. P and S, however, varied allometrically with seed mass. Additionally, seed mass only explained 37·3 % and 37·6 % of the total variance in P and S content, respectively. Seeds with higher mass contained proportionately more P and, furthermore, the seeds from small broods contained proportionally more P than those from large broods.

Conclusions

Although seed mass in this species can be used as a surrogate of investment in C and N, it does not account for variability in allocation of nutrients such as P and S. The fact that larger seeds increased their P concentration when found in smaller broods might be a consequence of intense competition for this nutrient among developing seeds. Then, brood size may influence the mineral nutrient concentration of seeds.     

Changes in incubation sharing in one pair of captive California condors (Gymnogyps californianus)

Three years of behavioral data were collected on incubation behavior in one pair of captive condors (Gymnogyps californianus) at the San Diego Wild Animal Park. Data were collected from daily video tape reviews of the nest box. The amount of time each bird was in the nest box, and whether it was on or off the egg were recorded, along with any aggressive interactions observed in the nest. For the first 2 years, the female incubated the egg(s) significantly more than the male. During the third year, the male increased his incubation time on the egg, resulting in no difference between the two sexes in incubation time. Changes in male incubation behavior may be a result of several factors: increased compatibility between the pair, social maturation, and/or increased dominance on the part of the male. © 1994 Wiley-Liss, Inc.     

Reproductive biology of captive Arabian oryx (Oryx leucoryx) in Saudi Arabia

Reproductive data on captive Arabian oryx (Oryx leucoryx) were collected from June 1986 through April 1992 at the National Wildlife Research Center (Taif, Saudi Arabia). Oryx females are polyestrous. The estrous cycle averaged 22 days and mean gestation length was 260 ± 5.5 days (S.D). Sex ratio at birth was unbiased and mean weight was 6.5 ± 0.7 kg (S.D.), with no difference between sexes. Under captive breeding conditions, births occurred throughout the year. Females gave birth to a single calf at any time during the day and produced 1.03 young per year. Abortion rate was 3.6%. Mortality rate of young was 6.1% before weaning at 3 months of age. The interbirth interval averaged 295 ± 42 days (S.D.), with 53% lasting between 270 and 279 days. Females reached sexual maturity at the age of 13 months. © 1996 Wiley-Liss, Inc.     

Reproduction in captive lion tamarins (Leontopithecus): Seasonality,infant survival,and sex ratios

Diversity in reproductive and social systems characterizes the primate family Callitrichidae. This paper contributes to our appreciation of this diversity by presenting the first detailed comparative analysis of captive breeding in three species of lion tamarins (Leontopithecus chrysomelas, L. chrysopygus, and L. rosalia) housed at the Centro de Primatologia do Rio de Janeiro. The annual pattern of reproduction in all three species of Leontopithecus was markedly seasonal, with births occurring during the spring, summer, and fall months from August through March. While modal number of litters produced per female per year was 1, approximately 20% of breeding females produced two litters per year. The onset of breeding activity in years when two litters are produced was significantly earlier than in years when only one litter was produced. The cumulative number of offspring surviving to 3 months of age did not differ between years with one vs. two breeding attempts. Like other callitrichids, postnatal mortality was highest during the first week of life, and there were pronounced species differences in offspring survival through 1 year, with significantly lower survivorship in L. chrysomelas. Infant survivorship was affected by a number of experiential factors. Survivorship up to 30 days of life was higher in groups in which the breeding female had previous experience with infants as a nonbreeding helper than in groups in which the female lacked previous helping experience. Likewise, survivorship to 30 days of life was higher for infants born to multiparous females than for infants born to primiparous females. When parity and previous helping experience were analyzed concurrently, the lowest survivorship was associated with offspring produced by inexperienced primiparous females. Genus-wide, there was no significant departure from a 50:50 sex ratio at any point during the first year of life, nor was there evidence for differential mortality for male and female infants. However, L. chrysopygus produced significantly more male infants at birth (65:44) and had male-biased litters (approximately 60% males) throughout the first year of life, while L. chrysomelas showed a nonsignificant tendency toward female-biased litters. © 1996 Wiley-Liss, Inc.     

Species diversity of bats (Mammalia: Chiroptera) in Iwokrama Forest, Guyana, and the Guianan subregion: implications for conservation

Fourteen species of bats are reported for the first time from Guyana (Saccopteryx gymnura, Micronycteris brachyotis, M. homezi, Lichonycteris obscura, Anoura latidens, Vampyressa pusilla, Vampyrodes caraccioli, Eptesicus chiriquinus, Cynomops paranus, Molossops neglectus, Molossus sp., Molossus coibensis, Molossus sinaloae, and Promops centralis) bringing the known bat diversity for the country to 121 species. Information including measurements, reproductive data, distribution, and taxonomy are provided for these species. Seven of these new records were collected in the Iwokrama International Rain Forest Programme site in central Guyana. Eighty-six bat species are now documented from Iwokrama Forest which is the highest species diversity for bats reported from any protected area in the world. There are, however, few tropical sites that have relatively complete inventories. A summary for bat species diversity in southern Venezuela, Guyana, Suriname, and French Guiana indicates that at least 146 species of bats are known from the Guianan subregion. Intense inventory surveys, especially in the often neglected subcanopy, suggest that species richness is probably underestimated in most Neotropical areas. Likewise, species-level diversity in the Guianan subregion is higher than previously suggested. Surveying and monitoring biodiversity are critical to developing a National Protected Areas System in Guyana.