Semi-natural Enclosure Research Articles

Altitudinal variation in thermal vulnerability of Qinghai-Tibetan Plateau lizards under climate warming

Abstract The survival of ectotherms worldwide is threatened by climate change. Whether increasing temperatures increase the vulnerability of ectotherms inhabiting temperate plateau areas remains unclear. To understand altitudinal variation in the vulnerability of plateau ectotherms to climate warming, Qinghai toad-headed lizards (Phrynocephalus vlangalii) were subjected to semi-natural enclosure experiments with simulated warming at high (2,600 m) and superhigh (3,600 m) elevations of the Dangjin Mountain, China. Our results revealed that the thermoregulatory effectiveness and warming tolerance (WT) of the toad-headed lizards were significantly affected by climate warming at both elevations, but their thermal sensitivity remained unchanged. After warming, the thermoregulatory effectiveness of lizards at superhigh elevations decreased because of the improved environmental thermal quality, whereas that of lizards at high-elevation conditions increased. Although the body temperature selected by high-elevation lizards was also significantly increased, the proportion of their active body temperature falling within the set-point temperature range decreased. This indicates that it is difficult for high-elevation lizards to adjust their body temperatures within a comfortable range under climate warming. Variations in the WT and thermal safety margin (TSM) under climate warming revealed that lizards at the superhigh elevation benefited from improved environmental thermal quality, whereas those at the high elevation originally on the edge of the TSM faced more severe threats and became more vulnerable. Our study highlights the importance of thermal biological traits in evaluating the vulnerability of ectotherms in temperate plateau regions.

Food preference strategy of four sympatric rodents in a temperate forest in northeast China.

Rodents are well known as both seed predators and dispersers of various plant species in forest ecosystems, and they play an important role in the regeneration of vegetation. Thus, the research on seed selection and vegetation regeneration by sympatric rodents is an interesting topic. To understand the characteristics of preferences of rodents for different seeds, a semi-natural enclosure experiment was performed with four rodent species (Apodemuspeninsulae, Apodemusagrarius, Tscherskiatriton, and Clethrionomysrufocanus) and the seeds of seven plant species (Pinuskoraiensis, Corylusmandshurica, Quercusmongolica, Juglansmandshurica, Armeniacasibirica, Prunussalicina, and Cerasustomentosa) to investigate the differentiation in niches and patterns of resource utilization of sympatric rodents. The results showed that all the rodents had consumed many seeds of Pi.koraiensis, Co.mandshurica, and Q.mongolica but differed significantly in how they selected the different seeds. The rate of utilization (Ri) of Pi.koraiensis, Co.mandshurica, and Q.mongolica exhibited the highest values. The Ei values indicated that the rodents tested exhibited differences in their priorities used to select the seeds from different plant species. All four species of rodents exhibited obvious preferences for certain seeds. Korean field mice preferentially consumed the seeds of Q.mongolica, Co.mandshurica, and Pi.koraiensis. Striped field mice favor the seeds of Co.mandshurica, Q.mongolica, P.koraiensis, and Nanking cherry. Greater long-tailed hamsters prefer to consume the seeds of Pi.koraiensis, Co.mandshurica, Q.mongolica, Pr.salicina, and Ce.tomentosa. Clethrionomysrufocanus likes to eat the seeds of Pi.koraiensis, Q.mongolica, Co.mandshurica, and Ce.tomentosa. The results supported our hypothesis that sympatric rodents overlap in food selection. However, each rodent species has a marked preference for food selection, and different rodent species differ in their food preferences. This reflects the role of distinct food niche differentiation in their coexistence.

Asymmetric competition for seeds between two sympatric food hoarding rodents: implications for coexistence.

Asymmetric competition occurs when some species have distinct advantages over their competitors and is common in animals with overlapping habitats and diet. However, the mechanism allowing coexistence between asymmetric competitors is not fully clear. Chinese white-bellied rats (Niviventer confucianus, CWR) and Korean field mice (Apodemus peninsulae, KFM) are common asymmetric competitors in shrublands and forests west of Beijing city. They share similar diet (e.g. plant seeds) and activity (nocturnal), but differ in body size (CWR are bigger than KFM), food hoarding habit (CWR: mainly larder hoarding; KFM: both larder and scatter hoarding), and ability to protect cached food (CWR are more aggressive than KFM). Here, we tested seed competition in 15 CWR-KFM pairs over a 10-day period under semi-natural enclosure conditions to uncover the differences in food hoarding, cache pilferage, and food protection between the 2 rodents, and discuss the implication for coexistence. Prior to pilferage, CWR harvested and ate more seeds than KFM. CWR tended to larder hoard seeds, whereas KFM preferred to scatter hoard seeds. Following pilferage, CWR increased consumption, decreased intensity of hoarding, and pilfered more caches from KFM than they lost, while KFM increased consumption more than they hoarded, and they preferred to hoard seeds in low and medium competition areas. Accordingly, both of the 2 rodent species increased their total energy consumption and hoarding following pilferage. Both rodent species tended to harvest seeds from the source, rather than pilfer caches from each other to compensate for cache loss via pilferage. Compared to CWR, KFM consumed fewer seeds when considering seed number, but hoarded more seeds when considering the seeds' relative energy (energy of hoarded seeds/rodent body mass2/3 ) at the end of the trials. These results suggest that asymmetric competition for food exists between CWR and KFM, but differentiation in hoarding behavior could help the subordinate species (i.e. KFM) hoard more energy than the dominant species (i.e. CWR), and may contribute to their coexistence in the field.

Gut microbiota reflect the crowding stress of space shortage, physical and non-physical contact in Brandt’s voles (Lasiopodomys brandtii)

Density-dependence plays a critical role in behavior and population regulation of small mammals, which is likely mediated by hormones and gut microbiota. High density-induced crowding effects often cause a combination of various social stresses including space shortage, physical contact and non-physical contact, but their distinct effects on gut microbiota in animals have not been investigated. In this study, we examined the crowding effects of space shortage and physical or non-physical contact stress on serum corticosterone and gut microbiota of Brandt’s voles in both laboratory and field conditions. Our results demonstrated that the space shortage stress showed a more predominant impact on serum corticosterone and gut microbiota of voles than physical or non-physical contact stress; the crowding effects of non-physical contact stress became stronger in high density conditions, while physical contact stress was stronger in a larger group without density effects. High density or group size treatments under both laboratory and semi-natural enclosure conditions significantly increased the relative abundance of key differential taxa, including Bacteroidetes, TM7, S24_7, Streptococcus, and Lactobacillus; while high density or group size treatments decreased the relative abundance of Firmicutes, Staphylococcaceae, Bacteroides, Faecalibacterium, and Adlercreutzia. Our study suggests that high density-induced space shortage and physical contact or non-physical contact stress may play a significant role in behavior and population regulation through altering gut microbiota in small mammals. Our results may also have significant implications in rodent control or health management for livestock.

Seed traits and rodent community interact to determine seed fate: evidence from both enclosure and field experiments.

Animal-mediated seed dispersal is an important ecological process in which a strong mutualism between animals and plants can arise. However, few studies have examined how a community of potential seed dispersers interacts with sympatric seed trees. We employed a series of experiments in the Qinling Mountains in both semi-natural enclosure and the field to assess the interactions among 3 sympatric rodent species and 3 Fagaceae tree seeds. Seed traits all showed similar tannin levels but markedly different physical traits and nutritional contents. We found that seeds with heavy weight, thick coat, and high nutritional contents were less likely to be eaten in situ but more often to be eaten after dispersal or hoarded by rodents. These results support both the handling time hypothesis and the high nutrition hypothesis. Surprisingly, we also found that rodents, maybe, preferred to consume seeds with low levels of crude fiber in situ, and to harvest and hoard those with high levels of crude fiber for later consumption. The sympatric rodent species, Cansumys canus, the largest rodent in our study, harvested and hoarded more Quercus variabilis seeds with high physical and nutritional traits, while Apodemus draco, the smallest rodent, harvested more Q. serrata seeds with low physical and nutritional traits, and Niviventer confucianus harvested and hoarded more Q. aliena seeds with medium physical and nutritional traits. Our study demonstrates that different seed traits play different roles in influencing the seed fate and the shaping of mutualism and predation interactions within a community of rodent species.

Courtship and underwater communication in the Sunda gharial (Tomistoma schlegelii)

ABSTRACT Many threatened crocodilians are shy and difficult to observe in the wild, limiting the current knowledge of their behaviour and ecology. Although acoustic communication is commonly used by adults during courtship and territory defence, the signals produced vary between taxa. Here we provide the first classification of adult vocalisations in Tomistoma schlegelii – a rare gavialid inhabiting swamp forests in Southeast Asia – and describe the behaviour produced during courtship. Using video and passive underwater acoustic monitoring we recorded a breeding captive pair of T. schlegelii housed indoors, as well as monitored 12 captive adults kept in a semi-natural outdoor enclosure over a period of two months. Courtship behaviour during 18 recorded mating events followed that observed in other crocodilians, but acoustic signals were restricted to mating activity and were only recorded in the two animals housed indoors. We identified seven signal types produced by T. schlegelii, which differed in duration, dominant frequency, and the presence of harmonic structure. These results suggest the species uses short-range, underwater acoustic signals during courtship and mating, with little vocal activity outside of those events, and provide foundation for future studies of this rare crocodilian.

Classifying and inferring behaviors using real-time acceleration biotelemetry in reproductive steelhead trout (Oncorhynchus mykiss).

Movement behaviors are central to ecology and conservation. Movement sensing technologies can monitor behaviors that are otherwise difficult to observe under field conditions and may enhance the ability to quantify behaviors at the population scale. We monitored steelhead trout (Oncorhynchus mykiss) spawning behaviors in a seminatural enclosure using accelerometer telemetry tags while simultaneously observing behaviors with underwater cameras. Behavioral assignments from visual observations were compared to acceleration histories to develop assignment criteria for acceleration data, including for a key behavior (oviposition). Behavioral events independently classified using acceleration data prior to reviewing video were compared to video scoring and 97% of holding behaviors, 93% of digging behaviors, and 86% of oviposition/covering behaviors were correctly assigned using acceleration data alone. We applied the method to at‐liberty steelhead in spawning tributaries. Acceleration records revealed putative spawning and oviposition in at‐liberty female steelhead, and time budgets for at‐liberty steelhead were similar to those monitored within enclosures. The use of similar movement sensing tags and classification approaches offers a method for monitoring movement behavior, activity budgets, and habitat use in a broad array of aquatic and terrestrial taxa, and may be especially useful when behaviors are cryptic.

Kinship analysis reveals reproductive success skewed toward overwintered Brandt's voles in semi-natural enclosures.

Age structure and seasonality influence the population fluctuations of small rodents. Age determines body weight and social experience, while seasonality regulates the duration of the breeding season and onset of sexual maturity in newborn offspring. Therefore, reproductive success and skew usually occur in different age groups. Brandt's vole (Lasiopodomys brandtii) is a social, short-lived and seasonal breeding small rodent with a dramatic seasonal population fluctuation, but reproductive skew is not fully understood in this species. In the present study, we determined kinship in semi-natural enclosure populations using microsatellite markers based on genotyping, analyzed the reproductive skew between sexes and between overwintered and newborn voles, and monitored variation in male reproductive activity by testing fecal testosterone levels throughout the year. Overwintered voles had the most reproductive success along with a striking increase in the population size in the enclosures, with all biological fathers and 77.8% of biological mothers, which had 100% and 87% of the total offspring, respectively. Compared to overwintered voles, reproductive skews were significantly higher in potential overwintered and newborn parents, implying the possible reproductive suppression of newborn voles by dominant overwintered voles. Moreover, both heavier body weight and higher testosterone levels in overwintered males supported their potential social status in the population. Our study provided new evidence for reproductive skew and differentiation of postnatal gonadal development patterns of different age groups in Brandt's vole.

Does intraspecific competition among Allenby’s gerbils lead to an Ideal Free Distribution across foraging patches?

Employing the Ideal Free Distribution (IFD) principle as a tool, we investigated how Allenby’s gerbils (Gerbillus andersoni allenbyi) utilized food patches within and moved between connected quadrants (i.e., ‘habitats’) in a large outdoor semi-natural enclosure. These habitats differed in initial forager densities, but provided equal numbers of standardized food patches that provided equal rewards (i.e. food) and costs (i.e. predation risk, metabolic, and missed opportunity). We quantified the gerbils’ giving-up-densities (GUDs) within foraging patches and recorded their daily distribution between habitats. Individual gerbils were tagged with unique bar-coded numbers to compare their locations within and across habitats. The mean number of gerbil foragers (9.1 and 8.9 individuals, respectively) and GUDs evened out across habitats over time. Despite this, the distribution of gerbils did not remain static within foraging patches; instead, gerbils altered their use of patches across and within habitats on a nightly basis. This may be due to a combination of factors including, high levels of interference competition between foragers at patches, a lag effect before the gerbils perceived changes in competition intensity with the arrival and departure of individuals, and gerbils having imperfect knowledge of their environment. Furthermore, the pattern of microhabitat (open vs bush patches) use by gerbils differed over time, indicating that despite the distribution of gerbils and their GUDs evening out between habitats, they still preferred foraging from safer bush patches over riskier open patches. This study provides insights into how under low predation risk, strong levels of intraspecific competition can shape the distribution of foragers across and within habitats.

Effects of insect infestation on rodent-mediated dispersal of Quercus aliena: results from field and enclosure experiments.

Rodents influence plant establishment and regeneration by functioning as both seed predators and dispersers. However, these rodent-plant interactions can vary significantly due to various environmental conditions and the activity of other insect seed predators. Here, we use a combination of both field and enclosure (i.e. individual cage and semi-natural enclosure) experiments, to determine whether rodents can distinguish sound seeds from those infested with insects. We also demonstrate how such responses to insects are influenced by food abundance and other environmental factors. We presented rodents with 2 kinds of Quercus aliena seeds (sound and insect-infested seeds) in a subtropical forest in the Qinling Mountains, central China, from September to November of 2011 to 2013. The results showed that rodents preferred to hoard and eat sound seeds than infested seeds in the field and semi-natural enclosure, while they preferred to eat infested seeds over sound seeds in the individual cages. In addition, both hoarding and eating decisions were influenced by food abundance. Rodents hoarded more sound seeds in years of high food abundance while they consumed more acorns in years of food shortage. Compared with field results, rodents reduced scatter-hoarding behavior in semi-natural enclosures and ate more insect-infested seeds in smaller individual cages. These results further confirm that rodents distinguish infested seeds from non-infested seeds but demonstrate that this behavior varies with conditions (i.e. environment and food abundance). We suggest that such interactions will influence the dispersal and natural regeneration of seeds as well as predation rates on insect larvae.

Differential seed mass selection on hoarding decisions among three sympatric rodents

Seed mass plays an important role in seed dispersal of many plant species during the hoarding process by rodents. Seeds of a particular plant species are usually dispersed by several sympatric rodent species. However, little is known about seed mass selection by different sympatric rodents that may show different hoarding behavior. In order to understand the role of different rodent species on the evolution of seed mass, we investigated the hoarding behavior and seed mass selection by three sympatric rodents (red spiny rat Maxomys surifer, Chinese white-bellied rat Niviventer confucianus, and yellow-bellied rat Rattus flavipectus) in semi-natural enclosures in southwest China. The hoarding behavior differed significantly among species: M. surifer showed predominantly scatter-hoarding behavior, N. confucianus showed both scatter- and larder-hoarding behavior, and R. flavipectus showed predominantly larder-hoarding behavior. All three rodent species preferred to remove and larder-hoard heavy seeds, but M. surifer and R. flavipectus were more selective on seed mass than N. confucianus during seed removal, while R. flavipectus were more selective than M. surifer and N. confucianus during larder-hoarding. The rodents showed contrasting preferences for seed mass during scatter-hoarding process. M. surifer and N. confucianus preferred to scatter-hoard heavy seeds, whereas R. flavipectus preferred to scatter-hoard light seeds. Our results show that different rodents may exert different selective pressures on seed mass during different dispersal processes. Changes in the composition of rodent communities, including those caused by human disturbance such as forest fragmentation, may influence the fates of seeds with different mass and the evolution of seed mass. Seed mass plays an important role in seed dispersal of many plants by scatter-hoarding rodents. Previous studies usually focus on seed-mass selection by the whole rodent community while ignore the interspecific variation; and they often obtain inconsistent results. By using the semi-natural enclosure, we detected differences in hoarding behaviors among sympatric rodent species, and their different preferences on seed mass. These different preferences may exert different selective pressures on seed mass. Changes in the composition of rodent communities may influence the fates of seeds with different mass and the evolution of seed mass. We suggest that differences in hoarding behavior among sympatric rodent species should be considered in future field studies, as this will help us to better understand the role of the whole rodent community in the evolution of seed mass of forest trees that depend on dispersal by rodents.

Scatter-hoarding rodents are better pilferers than larder-hoarders

Food hoarding is critical to rodents for their survival and reproduction. However, the seeds cached by rodents often suffer heavy pilferage by competitors. Therefore, compensation for cache loss is crucial, especially for scatter-hoarding rodents, as they cannot aggressively defend their stored seeds, whereas larder-hoarding rodents can. Pilfering caches of other individuals may be an effective way to compensate for cache loss for rodents. Hence, cache pilfering is likely to be as important as hoarding to food-hoarding rodents. Scatter-hoarding rodents may rely on their olfactory abilities and explore a wide area to retrieve their cached seeds, which may help to increase the probability of encountering and pilfering others' caches, whereas it is not essential for larder-hoarding rodents. We hypothesized that rodents that showed stronger scatter-hoarding behaviour would be better pilferers. To test this hypothesis, we investigated the relationship between scatter-hoarding and pilferage behaviours among four coexisting species of rodents using seminatural enclosure experiments in southwest China. Both hoarding and cache pilfering differed significantly between the four species. The predominant scatter-hoarding rodents, red spiny rats, Maxomys surifer, had a strong cache-pilfering behaviour, whereas yellow-bellied rats, Rattus flavipectus, mainly adopted larder-hoarding strategies and had a weak cache-pilfering behaviour. Chinese white-bellied rats, Niviventer confucianus, and chestnut rats, Niviventer fulvescens, had moderate scatter-hoarding and cache-pilfering behaviours. The intensity of cache pilfering was negatively correlated with the intensity of larder hoarding, but positively correlated with the intensity of scatter hoarding among the coexisting food-hoarding rodents. Our study suggests that the positive correlation between the intensities of scatter hoarding and cache pilfering is likely to facilitate reciprocal pilferage among scatter-hoarding rodents, which helps to maintain the stability of scatter-hoarding behaviour in these populations.

Seed trait-mediated selection by rodents affects mutualistic interactions and seedling recruitment of co-occurring tree species

As mutualists, seed dispersers may significantly affect mutualistic interactions and seedling recruitment of sympatric plants that share similar seed dispersers, but studies are rare. Here, we compared seed dispersal fitness in two co-occurring plant species (Armeniaca sibirica and Amygdalus davidiana) that inhabit warm temperate deciduous forest in northern China. We tested the hypothesis that seed trait-mediated selection by rodents may influence mutualistic interactions with rodents and then seedling establishment of co-occurring plant species. A.davidiana seeds are larger and harder (thick endocarps) than A.sibirica seeds, but they have similar levels of nutrients (crude fat, crude protein), caloric value and tannin. More A.sibirica seedlings are found in the field. Semi-natural enclosure tests indicated that the two seed species were both harvested by the same six rodent species, but that A.sibirica had mutualistic interactions (scatter hoarding) with four rodent species (Apodemus peninsulae, A. agrarius, Sciurotamias davidianus, Tamias sibiricus), and A.davidiana with only one (S. davidianus). Tagged seed dispersal experiments in the field indicated that more A.sibirica seeds were scatter-hoarded by rodents, and more A.sibirica seeds survived to the next spring and became seedlings. A.sibirica seeds derive more benefit from seed dispersal by rodents than A.davidiana seeds, particularly in years with limited seed dispersers, which well explained the higher seedling recruitment of A.sibirica compared with that of A.davidiana under natural conditions. Our results suggest that seed dispersers may play a significant role in seedling recruitment and indirect competition between co-occurring plant species.

Differences in alarm calls of juvenile and adult European ground squirrels (Spermophilus citellus): Findings on permanently marked animals from a semi-natural enclosure.

The European ground squirrel (Spermophilus citellus) emits alarm calls that warn conspecifics of potential danger. Although it has been observed that inexperienced juveniles of this species emit alarm calls that sound similar to those of adults, studies focusing on juvenile alarm calls are lacking. We analyzed the acoustic structure of alarm calls emitted by six permanently marked European ground squirrels living in a semi-natural enclosure when they were juveniles and after 1 year as adults. We found that the acoustic structure of the juvenile alarm calls was significantly different from those of adults and that the alarm calls underwent nearly the same changes in all studied individuals. All juveniles emitted alarm calls consisting of one element with almost constant frequency, but their alarm calls included a second frequency-modulated element after their first hibernation as adults. Our data show that the duration of the first element is significantly shorter in adults than in juveniles. Additionally, the frequency of the first element is significantly higher in adults than in juveniles. Similar to previous findings in other Palearctic ground squirrel species, our data are inconsistent with the assumption that juvenile mammals emit vocalizations with higher fundamental frequencies than adults. However, our results do not support the previously suggested hypothesis that juvenile ground squirrels conceal information regarding their age in their alarm calls because we found significant differences in alarm calls of juveniles and adults.

Seed trait and rodent species determine seed dispersal and predation: evidences from semi-natural enclosures

Abstract: Seed traits affect seed dispersal by animals. However, the combined role of seeds and dispersers in determining seed dispersal is not well explored. We attempted to test how seed traits and predators determine seed dispersal and predation interaction in a rodent-mediated seed dispersal system. Semi-natural enclosure experiments were conducted to investigate seed dispersal and predation of five sympatric tree species with different seed traits, Juglans mandshurica, Quercus mongolica, Pinus koraiensis, Corylus mandshurica and C. heterophylla by three rodent species, Apodemus peninsulae, Tamias sibiricus and Clethrionomys rufocanus showing different body sizes, hoarding behaviors and activity rhythms. Our results demonstrated that seed species with thick coat were removed more slowly than thin-coated seeds in regardless of rodent species, reflecting a consistent negative effect of seed coat on seed dispersal. Seeds with thick coat were less likely to be eaten both in situ and after removal by small rodents. Seeds with high caloric value were more likely to be larder-hoarded, whereas seed traits showed no influence on scatter-hoarding. Rodent species with large body size tended to eat more seeds in situ, while small-sized rodents preferred to eat seeds after removal. Large-sized rodent species scatter-hoarded more seeds, however, small-sized rodents larder-hoarded more seeds. Seeds with thick coat showed high mutualism but low predation with rodents, while rodents with large size showed low mutualism but high predation with seeds. Our results indicate that both seeds and predators play important roles in determining seed dispersal and predation in the seed-rodent dispersal system.

Scatter hoarding and hippocampal cell proliferation in Siberian chipmunks

Food hoarding, especially scatter hoarding and retrieving food caches, requires spatial learning and memory and is an adaptive behavior important for an animal’s survival and reproductive success. In the present study, we examined the effects of hoarding behavior on cell proliferation and survival in the hippocampus of male and female Siberian chipmunks (Tamias sibiricus). We found that chipmunks in a semi-natural enclosure displayed hoarding behavior with large individual variations. Males ate more scatter-hoarded seeds than females. In addition, the display of hoarding behavior was associated with increased cell proliferation in the hippocampus and this increase occurred in a brain region-specific manner. These data provide further evidence to support the notion that new cells in the adult hippocampus are affected by learning and memory tasks and may play an important role in adaptive behavior.

Behaviors of the Oriental White Stork (Ciconia boyciana) in a semi-natural enclosure

Environmental factors affect animal behavior in a variety of ways. Compared to animals in the wild, captive animals are kept in narrow enclosures, suffer higher densities and are more intensely affected by human activities. Therefore, behavioral elasticity is likely modified to some extent in cap- tive animals, which may negatively affect the possibility of successful release of endangered species in the wild. In our study we investigated the behaviors of the Oriental White Stork (Ciconia boyciana) in a semi-natural enclosure from 15 October 2005 to 8 September 2006 in Hefei Wildlife Park, China. The behavioral data were collected by instantaneous and scan sampling methods, and we analyzed the relationships between environmental factors and their behaviors. The amounts of time spent on maintenance behavior (foraging and moving) were at similar levels for birds reproducing multi- broods (Group 1), birds reproducing one brood (Group 2) and birds without reproduction (Group 3). On the other hand, the amount of time spent on elastic behavior (defensive, breeding and preen- ing) for Group 3 was lower than that for Groups 1 and 2. The behavioral pattern of the storks exhib- ited marked seasonal changes, which may be a function of ambient temperature, human disturbanc, and the length of daylight, but not of wind intensity. Our results provide basic data for future conser- vation measures of this endangered species.

Energy, water and space use by free-living red kangaroos Macropus rufus and domestic sheep Ovis aries in an Australian rangeland

We used doubly labelled water to measure field metabolic rates (FMR) and water turnover rates (WTR) in one of Australia's largest native herbivores, the red kangaroo (Macropus rufus) and one of Australia's dominant livestock species, the wool-breed Merino sheep, under free-living conditions in a typical Australian rangeland. Also, we used GPS technology to examine animal space use, along with the comparisons of urine concentration, diet, diet digestibility, and subsequent grazing pressures. We found smaller space-use patterns than previously reported for kangaroos, which were between 14 and 25% those of sheep. The FMR of a 25-kg kangaroo was 30% that of a 45-kg sheep, while WTR was 15% and both were associated with smaller travel distances, lower salt intakes, and higher urine concentration in kangaroos than sheep. After accounting for differences in dry matter digestibility of food eaten by kangaroos (51%) and sheep (58%), the relative grazing pressure of a standard (mature, non-reproductive) 25-kg kangaroo was 35% that of a 45-kg sheep. Even for animals of the same body mass (35kg), the relative grazing pressure of the kangaroo was estimated to be only 44% that of the sheep. After accounting for the energetic costs of wool growth by sheep, the FMRs of our sheep and kangaroos were 2-3 times their expected BMRs, which is typical for mammalian FMR:BMRs generally. Notably, data collected from our free-living animals were practically identical to those from animals confined to a semi-natural enclosure (collected in an earlier study under comparable environmental conditions), supporting the idea that FMRs are relatively constrained within species.

Seed caching and cache pilferage by three rodent species in a temperate forest in the Xiaoxinganling Mountains

Although differences in food-hoarding tactics both reflect a behavioral response to cache pilferage among rodent species and may help explain their coexistence, differentiation in cache pilfering abilities among sympatric rodents with different hoarding strategies is seldom addressed. We carried out semi-natural enclosure experiments to investigate seed hoarding tactics among three sympatric rodent species (Tamias sibiricus, Apodemus peninsulae and Clethrionomys rufocanus) and the relationship of their pilfering abilities at the inter- and intraspecific levels. Our results showed that T. sibiricus exhibited a relatively stronger pilfering ability than A. peninsulae and C. rufocanus, as indicated by its higher recovery rate of artificial caches. Meanwhile A. peninsulae showed a medium pilfering ability and C. rufocanus displayed the lowest ability. We also noted that both cache size and cache depth significantly affected cache recovery in all three species. T. sibiricus scatter-hoarded more seeds than it larder-hoarded, A. peninsulae larder-hoarded more than scatter-hoarded, and C. rufocanus acted as a pure larder-hoarder. In T. sibiricus, individuals with lower pilfering abilities tended to scatter hoard seeds, indicating an intraspecific variation in hoarding propensity. Collectively, these results indicated that sympatric rodent species seem to deploy different food hoarding tactics that allow their coexistence in the temperate forests, suggesting a strong connection between hoarding strategy and pilfering ability.

Experimental study of dispersal behaviour in a wall lizard species (Podarcis sicula) (Sauria Lacertidae)

Movement behaviour and dispersal are key processes in biology because they represent a basic phase of the individual life-cycle with spin-offs for population dynamics, genetics and biogeography. Experimental studies have shown that the dispersal rate increases with density for a variety of taxa. Here we investigate the ecological aspects of animal movement and dispersal in a wall lizard species (Podarcis sicula), evaluating the short-term effects of increasing population density and individual conditions. The individual attitude on movement is assessed by comparing immigration between two alternative scenarios of augmentation (moderate starting density) and colonisation (high starting density) by using a connected semi-natural enclosure system. The main result of our study was that the patch density influenced the dispersal activity in the study species. Moreover, the movement rate between patches was sex-biased (higher in males), influenced by tail status, but not dependent upon body size and condition. The patch density drove the movement activity in the studied lizards (augmentation design), but there were also factors at individual level influencing the propensity to move (sex and tail status). In the studied lizard, individual decisions to leave a patch and settle in a new one are both condition-dependent – which means that individuals rely on a set of external cues to adjust their dispersal tactics – and phenotype-dependent – which means that dispersal propensity correlates with a suite of phenotypic traits.