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Preferences of pre-weanling Long-Evans rats for anal excreta of adult males and females.

Long-Evans hooded rat pups were reared with their dam alone, their dam and sire or their dam 12 hrs per day and their sire 12 hrs per day and tested for preferences for anal excreta from adult male and female rats when they were 18 to 20 days of age. In all rearing conditions the anal excreta of the rat's own dam was preferred to that of strange dams and the excreta of both own and strange dams was preferred to that of virgin females. Anal excreta from virgin females was preferred to no odor as was anal excreta of unmated males, strange sires and the rat's own sire. Only rats reared with their dam and sire preferred the odor of their own sire to that of other males. The results suggest that pre-weanling rats may attend to different dimensions of the odors of conspecifics, such as the species odor, maternal odor, and individual odor and that different rearing conditions may influence the odor dimension to which the rat attends.

Animals↗

Suppression of postpartum fertility in pairs of female rats sharing the same nesting environment.

The probability that a successful pregnancy will follow postpartum estrus in the rat is significantly reduced when the postpartum female is housed with another female that is both pregnant and lactating. We studied 16 pairs of females, each pair maintained in a separate nesting environment containing a sexually active male. In 12 of the pairs, the female that gave birth in the presence of a lactating-pregnant partner either did not mate, mated but failed to implant, resorbed her fetuses or delivered non-viable young. Several mechanisms that might underlie this evident suppression of fertility are discussed.

Animals↗

Telemetered temperature monitoring in preweanling Mongolian gerbils (Meriones unguiculatus).

Like most small mammals, Mongolian gerbils (Meriones unguiculatus) are born without the ability to maintain core body temperature (Tb). Breeding adults, juvenile alloparents, nest materials, and other litter mates probably contribute to the maintenance of core body temperature in neonates, but the relative role of each factor is unknown. We developed a procedure allowing biotransmitters to be implanted into 9-day-old pups for use with a radiotelemetry system. Experiment 1 demonstrated the development of thermoregulatory capacity over postpartum days 11, 15, and 19. Pups at 11 days of age lacked thermoregulatory capacity, and maintained Tb only slightly above the ambient temperature (15 degrees C) of the testing environment. The transition from poikilothermy to homeothermy was clearly accomplished by day 19, with pups maintaining Tb of 35.8 +/- 0.2 degrees C for at least 100 min. Experiment 2 measured Tb in 11- and 12-day-old pups during a thermal challenge (15 degrees C) in the presence of nest materials, litter mates, or both. Pups provided with either nest materials, litter mates, or both maintained higher Tb during a 40-min test than those without these resources. Our methodology minimizes disruptions and the thermal consequences associated with other invasive (rectal probe thermistors) and noninvasive (e.g., infrared thermography) procedures.

Animals↗

Is nest building an important component of thermoregulatory behaviour in the pouched mouse (Saccostomus campestris)?

The thermoregulatory significance of nest building in Saccostomus campestris was investigated by examining the effect of temperature and photoperiod on the size and thermal conductance of nests built within artificial burrows by pouched mice from four localities in southern Africa that experience contrasting thermal conditions. There was no correlation between the amount of nesting material used and the thermal conductance of nests, which indicates that nest size was not a reliable measure of nest quality. For this reason, the significant interactive effect of sex and locality on the quantity of nesting material used, and the significantly larger nests built by wild-caught animals, appear to be unrelated to differences in nesting ability, particularly as there were no similar differences in the thermal conductance of nests between these groups. Several animals blocked the entrance to their artificial burrows and caused a significant reduction in the rate of heat loss from nests therein. However, heat conservation may not have been the primary function of plugging burrow entrances because this did not occur more frequently at lower temperatures and was not more common among animals from cooler localities. Instead, animals that sealed the entrance to their burrows were found to hoard significantly more food than animals that left the entrance open, which suggests that burrows may have been blocked to prevent the potential theft of stored food. Despite substantial variability in both the size and thermal conductance of nests built throughout the present study, there was no significant effect of temperature, photoperiod, or locality on these characteristics.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

Pores in avian eggshells: gas conductance, gas exchange and embryonic growth rate.

The number of pores (N) in eggshells of birds were counted in 161 species ranging in egg mass (W) from 0.9 to 500 g. In addition the water vapor conductance of the shell (G) mg X (d X Torr)-1, the water loss in the nest (M) mg X d-1, the incubation duration (I) d, and the shell thickness or pore length (L) micron are listed for each species when available. Allometric equations for all variables are given when regressed on egg mass. When log G is regressed on log N the slope is essentially 1.0 indicating that the G X N-1 for average pores in bird eggshells is 1.5 micrograms H2O X (d X Torr)-1 regardless of egg mass or incubation duration. According to Fick's law of diffusion such pores have a cross-sectional area to pore length ratio of 0.67 micron 2 X micron-1. Further analysis show that N, G, M, and the rate of oxygen consumption at the pre-internal pipping stage, are all directly proportional to the absolute mean growth rate of embryos (defined as 0.67 [W/I], g X d-1). Thus, single pores of typical eggshells not only have a similar conductance G X N-1, but also the metabolic rate and rate of water loss are matched to the pore conductance so that O2, CO2 fluxes per pore at the pre-internal pipping stage and water vapor flux per pore are similar among species, namely 68, 49 and 50 microliters X d-1, respectively. The partial pressure differences across the shell at the same stage are 42, 40 and 27 Torr, respectively. Ecological as well as taxonomical variation may alter some of the relationships predicted for the 'typical' egg in order to conserve a typical overall diffusive water loss.

Animals↗

Nest ventilation explains gas composition in the nest-chamber of the European bee-eater.

The European bee-eater Merops apiaster builds a nest in soil banks comprising a horizontal corridor (159 cm) leading to a 3.4 L nest chamber. An adult and six eggs and/or nestlings occupy this nest for 60 d. Incubation and development are asynchronous. In order to evaluate the gas exchange pattern of the occupied nest, we measured the O2 diffusive conductance of the nest with the ambient environment (GNO2), its internal O2 and CO2 pressures (PNO2 and PNCO2), temperature (TN) and observed the sequences of development and the frequency of parental visits. We also measured the rate of O2 uptake (MO2) of the eggs, nestlings and adults. The GNO2 was 10.9 ml[STPD]/(h.Torr). The PNO2 dropped and the PNCO2 increased during incubation and growth to a maximal change of 24 and 23 Torr, respectively. Maximal MO2 of an egg and a nestling were 5.4 and 146 ml[STPD]/h, respectively. The MO2 of an adult at rest and at TN (27 degrees C) was 90.5 ml[STPD]/h. From clutch size, sequence of nest events, and the above values we have estimated a maximal nest chamber ventilation (VN) of 0.8 L/min necessary to prevent lowering PNO2 to 74 Torr below ambient PO2. This convection is achieved chiefly by the parental feeding visits (up to 40/h). Thus, movement along the corridor convects 1.2 L per visit.

Animals↗

Small passerines can discriminate ultraviolet surface colours.

Hollow-dwelling passerine birds were tested for UV surface colour discrimination by using the instinct to bring food to nestlings that makes a bird search for the nest under changing conditions. The experiments were carried out on breeding pairs of pied flycatcher (Muscicapa hypoleuca), great tit (Parus major) and tree sparrow (Passer montanus) in the wild by the method of alternative choice of entrance into a double nesting-box with the nestlings in one or the other section. The entrances were marked with sheets of painted papers that had different reflectances in UV. For a human observer, all marks looked achromatic. Birds were trained to discriminate the mark coloured with UV-absorbing paint from a neutral one (with equal reflectance throughout the spectrum). Birds easily learned to search for the UV-absorbing mark, and transferred the acquired habit when tested with new marks that differed only slightly from the initial ones in lightness to eliminate brightness cues.

Animals↗

Geotropic sensitivity of hornets.

Oriental Hornet workers, Vespa orientalis (Hymenoptera: Vespinae) were measured for their responses to changes in the direction of the gravitational field and this under both static and kinetic (centrifugal) conditions. The hornets can build a comb (oriented towards the gravitational force) when their multifaceted eyes are covered. Building activity is undertaken in the dark as well as by hornets that had been blinded or had eclosed in the dark and had never seen any light. If the frons plate of hornets is damaged, there is no or little building, and the comb direction is distorted. Hornets eclosing from and developing in combs subjected to centrifugal spinning build combs whose direction is affected both by rotation and by the resultant of the gravitational and centrifugal forces.

Animals↗

Metabolic cost of incubation in the Laysan albatross and Bonin petrel.

1. Oxygen consumption and carbon dioxide production were measured in resting and incubating Laysan albatrosses and Bonin petrels on Midway Atoll in the north central Pacific Ocean. 2. Incubation metabolism within the thermal neutral zone is less than or equal to resting metabolism in the albatross and petrel. 3. The respiratory quotients (0.64-0.72) during the long fasts indicate fat metabolism. 4. The estimated fractional water content of the albatross and petrel do not change during incubation fasts because water loss is balanced by metabolic water production.

Animals↗

Hornet building orientation in additional magnetic fields.

In artificial breeding boxes (ABBs), as in nature, hornet (Vespa orientalis) workers build combs oriented downwards connected by pedicles to the roof. The cells in such combs face downwards with a scatter angle of 3-14 degrees from the vertical. This vertical direction seems to be the result of the combined influence of both the gravitational force and the vertical component of the earth's magnetic field intensity vector. Hornet workers placed in ABBs in additional static magnetic fields, which compensated the vertical component of the earth's magnetic field vector, built small combs or single cells on the side walls, or on the floor. They initiated the cells in the horizontal direction. In the boxes where the compensating field was uniform the cells axes were directed horizontally, whereas in the boxes placed in a non-uniform compensating field, the cells were gradually oriented downwards. In very non-uniform horizontal additive fields with intensities of the same order of magnitude as that of the earth's field, hornets were disoriented. They built combs and single cells directing them towards the regions where the magnetic field was weakest, and even upwards.

Adaptation, Physiological↗

Blood parameters as consistent predictors of nestling performance in great tits (Parus major) in the wild.

Fourteen blood profile variables were analysed in 12-day-old nestlings of great tits (Parus major) in the wild. Except for plateletocrit and platelet distribution width, the traits showed a consistent pattern of variation, with significant intra-brood repeatabilities; they were shown to be significant predictors of nestling performance as measured by survival from hatching to fledging. It is concluded that all blood characteristics that show consistent within-brood variation may be useful as indicators of some aspects of nestling condition/health status in wild birds.

Animals↗

Hematological parameters in brood-rearing great tits in relation to habitat, multiple breeding and sex.

Very little is known about the causes and correlates for variation of individual condition in the wild. However, such knowledge is essential for understanding the mechanisms that mediate environmental effects to populations. We studied the variation of several hematological condition indices (hematocrit, albumin, globulin and triglyceride concentrations, albumin/globulin ratio, lymphocyte and heterophile concentrations and heterophile/lymphocyte ratio) and body mass in brood-rearing great tits (Parus major) in relation to habitat, multiple breeding and gender. Although great tits prefer deciduous forest to coniferous forests, individuals breeding in coniferous forests tended to be in a superior health state than those breeding in deciduous habitat. We suggest that this difference in adult condition can be caused by differences in breeding densities between habitats. Although there was some variation in condition indices between breeding attempts, none of these parameters measured at the end of the first breeding attempt predicted the probability of double breeding. We also found that females were in poorer condition and probably more stressed than males, both during the first and the second breeding attempt. These findings demonstrate that hematological parameters can be used to assess spatial and temporal variation of individual condition in the wild.

Animals↗

Egg components, egg size, and hatchling size in leatherback turtles.

Relationships between egg size, egg components, and neonate size have been investigated across a wide range of oviparous taxa. Differences in egg traits among taxa reflect not only phylogenetic differences, but also interactions between biotic (i.e., maternal resource allocation) and abiotic (i.e. nest environment conditions) factors. We examined relationships between egg mass, egg composition, and hatchling size in leatherback turtles (Dermochelys coriacea) because of the unique egg and reproductive characteristics of this species and of sea turtles in general. Albumen comprised 63.0%+/-2.8% (mean+/-S.D.) of egg mass and explained most of the variation in egg mass, whereas yolk comprised only 33.0%+/-2.7%. Additionally, leatherback albumen dry mass was approximately 16% of albumen wet mass. Whereas hatchling mass increased significantly with egg mass (n = 218 clutches), hatchling mass increased by only approximately 2 g for each 10 g increase in egg mass and was approximately 10-20 g greater than yolk mass. Taken together, our results indicate that albumen might play a particularly significant role in leatherback embryonic development, and that leatherback eggs are both capable of water uptake from the nest substrate and also possess a large reservoir of water in the albumen. Relationships between egg mass and egg components, such as variation in egg mass being largely explained by variation in albumen mass and egg mass containing a relatively high proportion of albumen solids, are more similar to bird eggs than to eggs of other non-avian reptiles. However, hatchling mass correlates more with yolk mass than with albumen mass, unlike patterns observed in bird eggs of similar composition.

Animals↗

A test of the thermal-stress and the cost-of-burrowing hypotheses among populations of the subterranean rodent Spalacopus cyanus.

Subterranean mammals show lower than-allometrically expected-basal metabolic rates (BMR), and several competing hypotheses were suggested to explain how physical microenvironmental conditions and underground life affect subterranean mammalian energetics. Two of these are the thermal-stress and the cost-of-burrowing hypotheses. The thermal-stress hypothesis posits that a lower mass-independent BMR reduces overheating in burrows where convective and evaporative heat loss is low, whereas the cost-of-burrowing hypothesis states that a lower mass-independent BMR may compensate for the extremely high energy expenditure of digging during foraging activity. In this paper we tested both hypotheses at an intraspecific level. We compared seven populations of the subterranean rodent Spalacopus cyanus or cururo from different geographic localities with contrasting habitat conditions. We measured BMR and digging metabolic rate (DMR) through open flow respirometry. Our results support neither the thermal-stress nor the cost-of-burrowing hypothesis. Cururos from habitats with contrasting climatic and soil conditions exhibited similar BMR and DMR when measured under similar semi-natural conditions. It is possible that S. cyanus originated in Andean locations where it adapted to relatively hard soils. Later, when populations moved into coastal areas characterized by softer soils, they may have retained the original adaptation without further phenotypic changes.

Animals↗

Evaluation of biochemical effects related to perfluorooctane sulfonic acid exposure in organohalogen-contaminated great tit (Parus major) and blue tit (Parus caeruleus) nestlings.

A perfluorooctane sulfonic acid (PFOS) biomonitoring survey was conducted on great tit (Parus major) and blue tit (Parus caeruleus) nestlings from Blokkersdijk, a bird reserve in the proximity of a fluorochemical plant in Antwerp (Belgium) and Fort IV, a control area. PFOS, together with 11 organochlorine pesticides, 20 polychlorinated biphenyl congeners and 7 polybrominated diphenyl ethers were measured in liver tissue. The hepatic PFOS concentrations at Blokkersdijk (86-2788 and 317-3322 ng/g wet weight (ww) for great and blue tit, respectively) were among the highest ever measured and were significantly higher than at the control area (17-206 and 69-514 ng/g ww for great and blue tit, respectively). The hepatic PFOS concentration was species- and sex-independent and correlated significantly and positively with the serum alanine aminotransferase activity and negatively with the serum cholesterol and triglyceride levels in both species but did not correlate with condition or serum protein concentration. In the great tit, a significant positive correlation was observed between the liver PFOS concentration and the relative liver weight. In the blue tit, the hepatic PFOS concentration correlated positively and significantly with hematocrite values. None of the investigated organohalogen pollutants except for PFOS were suggested to be involved in the observed biological alterations.

Alanine Transaminase↗