RSS 1.0Biological Sciences
The Department of Biological Sciences has an expanding research base, which, in addition to providing leading researchers of national and international standing in these areas, most importantly underpins the delivery of teaching. Research in Biological Sciences at Chester can be divided into three broad groups of expertise, namely Animal Behaviour and Conservation, Food Nutrition and Health, and Stress and Disease.
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Preliminary investigation of the effects of a concert on the behavior of zoo animalsTo increase visitor footfall and engagement, zoos may host public events which may extend outside of typical opening hours. With plans to hold a 2-day concert at Tayto Park, Ireland, this study aimed to identify the behavioral response to the music event of a selected group of species in the zoo. Twenty-two species were observed across three Phases of the event (pre-, during and post-event). Specific behaviors of interest were categorized as active, resting, asleep, abnormal, and out of sight, with repeated observations being made at each enclosure during each Phase. Alongside these behavioral data, Sound Pressure Levels (SPLs) were concurrently recorded at the observation locations in terms of both dB(A) and dB(C). The median dB(C) levels during the event were found to be significantly higher (mdn = 64.5dB) when compared with both pre- (mdn = 60.7dB) and post-event Phases (mdn = 59.4dB), whilst dB(A) levels were only significantly higher during the event (51.7dB) when compared with the pre-event Phase (mdn = 49.8dB). We found some species-specific behavioral changes (mainly associated with active and resting behaviors) correlated with increased SPLs and/or event itself. However, the behavioral responses varied between species and there were numerous species which did not respond with any change in behavior to the increased SPLs or the event itself. This variation in response across species reinforces the need for monitoring of behavioral changes as well as consideration of their natural behavioral ecology when implementing appropriate mitigation strategies. Further research should be encouraged to provide evidence-based assessment of how music events may affect animal welfare and behavior and to test the efficacy of mitigation strategies that are implemented to safeguard animal welfare.
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Human-controlled reproductive experience may contribute to incestuous behavior observed in reintroduced semi-feral stallions (Equus caballus)Equine reproductive behavior is affected by many factors, some remaining poorly understood. This study tested the hypothesis that a period of captivity during the juvenile period and human-controlled reproduction may potentially be involved in the disruption of the development of incestuous mating avoidance behavior in sanctuary-reintroduced male Konik polski horses. Between 1986 and 2000, cases of incestuous behavior in harem stallions born and reared until weaning in the sanctuary were studied. Eight males lived in the sanctuary’s feral herd for the rest of their lives (the non-captive group; nC). They gained their own harem of mares without human intervention (no human-controlled reproductive activity, nHC). Another five stallions were removed as weanlings, reared in captivity and then reintroduced as adults (captive, C). Three of these C stallions were used as in-hand breeding stallions, one as a “teaser” (human-controlled reproductive activity, HC) and one was not used for reproduction in captivity (nHC). Reproductive records for 46 mares, daughters of all 13 harem stallions, were scrutinized and cases of incestuous breeding were recorded by interrogation of foal parentage records. C stallions failed to expel more daughters than nC stallions (33% vs. 18%, P = 0.045), and mated with significantly more of them (28% vs. 11%, P = 0.025). Interestingly, HC stallions expelled fewer (60%) and successfully mated with more (33%) daughters that nHC stallions (84% expelled, P = 0.013, and 10% successful mating with daughters, P = 0.010). All HC stallions bred incestuously at least once. We propose that human intervention during a critical period of development of social and reproductive behavior in young stallions, by enforced separation from their natal herd and in-hand breeding, may contribute to their later aberrant behavior and disruption of inbreeding avoidance mechanisms in these stallions. The previous occurrence of human-controlled breeding may be one of the factors promoting incestuous behavior of stallions in natural conditions. The uninterrupted presence of stallions in their harems and herd member recognition may also play important roles in inbreeding avoidance in horses.
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ABO Blood Groups Do Not Predict Schistosoma mansoni Infection Profiles in Highly Endemic Villages of UgandaSchistosoma mansoni is a parasite which causes significant public-health issues, with over 240 million people infected globally. In Uganda alone, approximately 11.6 million people are affected. Despite over a decade of mass drug administration in this country, hyper-endemic hotspots persist, and individuals who are repeatedly heavily and rapidly reinfected are observed. Human blood-type antigens are known to play a role in the risk of infection for a variety of diseases, due to cross-reactivity between host antibodies and pathogenic antigens. There have been conflicting results on the effect of blood type on schistosomiasis infection and pathology. Moreover, the effect of blood type as a potential intrinsic host factor on S. mansoni prevalence, intensity, clearance, and reinfection dynamics and on co-infection risk remains unknown. Therefore, the epidemiological link between host blood type and S. mansoni infection dynamics was assessed in three hyper-endemic communities in Uganda. Longitudinal data incorporating repeated pretreatment S. mansoni infection intensities and clearance rates were used to analyse associations between blood groups in school-aged children. Soil-transmitted helminth coinfection status and biometric parameters were incorporated in a generalised linear mixed regression model including age, gender, and body mass index (BMI), which have previously been established as significant factors influencing the prevalence and intensity of schistosomiasis. The analysis revealed no associations between blood type and S. mansoni prevalence, infection intensity, clearance, reinfection, or coinfection. Variations in infection profiles were significantly different between the villages, and egg burden significantly decreased with age. While blood type has proven to be a predictor of several diseases, the data collected in this study indicate that it does not play a significant role in S. mansoni infection burdens in these high-endemicity communities.
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Behavioural Indicators of Intra- and Inter-Specific Competition: Sheep Co-Grazing with Guanaco in the Patagonian SteppeIn extensive livestock production, high densities may inhibit regulation processes, main- taining high levels of intraspecific competition over time. During competition, individuals typically modify their behaviours, particularly feeding and bite rates, which can therefore be used as indicators of competition. Over eight consecutive seasons, we investigated if variation in herd density, food availability, and the presence of a potential competitor, the guanaco (Lama guanicoe), was related with behavioural changes in domestic sheep in Chilean Patagonia. Focal sampling, instantaneous scan sampling, measures of bite and movement rates were used to quantify behavioural changes in domestic sheep. We found that food availability increased time spent feeding, while herd density was associated with an increase in vigilant behaviour and a decrease in bite rate, but only when food availability was low. Guanaco presence appeared to have no impact on sheep behaviour. Our results suggest that the observed behavioural changes in domestic sheep are more likely due to intraspecific competition rather than interspecific competition. Consideration of intraspecific competition where guanaco and sheep co-graze on pastures could allow management strategies to focus on herd density, according to rangeland carrying capacity.
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Marginal habitats provide unexpected survival benefits to the Alpine marmotAge-specific survival trajectories can vary significantly among wild populations. Identifying the environmental conditions associated with such variability is of primary importance to understand the dynamics of free-ranging populations. In this study, we investigated survival variations among alpine marmot (Marmota marmota) families living in areas with opposite environmental characteristics: the typical habitat of the species (alpine meadow) and a marginal area bordering the forest. We used data collected during an 11-year study in the Gran Paradiso National Park (Italy) and performed a Bayesian survival trajectory analysis on marked individuals. Furthermore, we investigated, at a territorial level, the relationships among demographic parameters and habitat variables by using a path analysis approach. Contrary to our expectations, for most of the marmot’s lifespan, survival rate was higher in the marginal site closer to the forest and with lower visibility than in the alpine meadow site. Path analysis indicated that the number of families living close to each other negatively affected the stability of the dominant couple, which in turn affected both juvenile survival and reproduction. Given the lower number of neighbouring families which inhabited the marginal site and the potentially different predation pressure by the most effective predator in the area (Aquila chrysaetos), our results suggest that species adapted to live in open habitats may benefit from living in a marginal habitat. This study highlights the importance of habitats bordering the forest in the conservation of alpine marmots.
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Heterospecific Fear and Avoidance Behaviour in Domestic Horses (Equus caballus)Ridden horses have been reported to be fearful of cows. We tested whether cows could provoke behavioural and cardiac fear responses in horses, and whether these responses differ in magnitude to those shown to other potential dangers. Twenty horses were exposed to cow, a mobile object or no object. The time spent at different distances from the stimulus was measured. In a separate test, heart rate (HR), root mean square of successive differences between heartbeats (RMSSD) and the horses’ perceived fear were assessed at various distances from the stimuli. The horses avoided the area nearest to all stimuli. During hand‐leading, the cow elicited the highest HR and lowest RMSSD. Led horses’ responses to the cow and box were rated as more fearful as the distance to the stimulus decreased. Mares had a higher HR than geldings across all tests. HR positively correlated with the fearfulness rating at the furthest distance from the cow and box, and RMSSD negatively correlated with this rating in cow and control conditions. Our results show that these horses’ avoidance response to cows was similar or higher to that shown towards a novel moving object, demonstrating that potentially, both neophobia and heterospecific communication play a role in this reaction.
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Sex and age-specific survival and life expectancy in a free ranging population of Indri indri (Gmelin, 1788).The critically endangered indri (Indri indri) is the largest extant lemur species and its population size is projected to decline over the next three generations due to habitat loss, hunting and climate change. Accurate information on the demographic parameters driving the population dynamics of indri is urgently needed to help decision-making regarding the conservation of this iconic species. We monitored and followed the life histories of 68 individually recognizable indris in 10 family groups in the Maromizaha New Protected Area (Madagascar) for 12 years. We estimated age and sex-specific survival trajectories using a Bayesian hierarchical survival model and found that the survival curves for male and female indris show a similar pattern, consistent with what found typically in primates; i.e., a high infant mortality rate which declines with age in the juvenile phase and increases again for adults. Also, life expectancies at 2 years of age (e2), were found to be similar between the sexes (e2 females = 7.8 years; e2 males = 7.5 years). We suggest that the lack of strong differences in the survival patterns for male and female indris are related to the strictly monogamous mating system and the lack of sexual dimorphism in this species. Our study provides, for the first time, robust estimates for demographic parameters of indris and one of the very few datasets on survival trajectories available for primates.
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Principal Component Analysis as a Novel Method for the Assessment of the Enclosure Use Patterns of Captive Livingstone’s Fruit Bats (Pteropus livingstonii)The Spread of Participation Index (SPI) is a standard tool for assessing the suitability of enclosure design by measuring how captive animals access space. This metric, however, lacks the precision to quantify individual-level space utilization or to determine how the distribution of resources and physical features within an enclosure might influence space use. Here we demonstrate how Principal Component Analysis (PCA) can be employed to address these aims and to therefore facilitate both individual-level welfare assessment and the fine-scale evaluation of enclosure design across a range of captive settings. We illustrate the application of this methodology by investigating enclosure use patterns of the Livingstone’s fruit bat (Pteropus livingstonii) population housed at Jersey Zoo. Focal sampling was used to estimate the time each of 44 individuals in the first data collection period and 50 individuals in the second period spent in each of 42 theoretical enclosure sections. PCA was then applied to reduce the 42 sections to five and seven ecologically relevant “enclosure dimensions” for the first and second data collection periods respectively. Individuals were then assigned to the dimension that most accurately represented their enclosure use patterns based on their highest dimensional eigenvalue. This assigned dimension is hereafter referred to as the individual’s Enclosure Use Style (EUS). Sex was found to be significantly correlated with an individual’s EUS in the second period, whilst age was found to significantly influence individual fidelity to assigned EUS. When assessing the effect of resource location on group-level preference for certain sections, the presence of feeders and proximity to public viewing areas in period one, and feeders and heaters in period two, were positively correlated with space use. Finally, individual EUS remained consistent between both data collection periods. We interpret these results for this species in the context of its observed behavioural ecology in the wild and evaluate the degree to which the current captive enclosure for this population allows for optimal individual welfare through the facilitation of spatial choice. We then explore how these methods could be applied to safeguard captive animal welfare across a range of other scenarios.
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Non-territorial GPS-tagged golden eagles Aquila chrysaetos at two Scottish wind farms: avoidance influenced by preferred habitat distribution, wind speed and blade motion statusWind farms can have two broad potential adverse effects on birds via antagonistic processes: displacement from the vicinity of turbines (avoidance), or death through collision with rotating turbine blades. These effects may not be mutually exclusive. Using detailed data from 99 turbines at two wind farms in central Scotland and thousands of GPS-telemetry data from dispersing golden eagles, we tested three hypotheses. Before-and-after-operation analyses supported the hypothesis of avoidance: displacement was reduced at turbine locations in more preferred habitat and with more preferred habitat nearby. After-operation analyses (i.e. from the period when turbines were operational) showed that at higher wind speeds and in highly preferred habitat eagles were less wary of turbines with motionless blades: rejecting our second hypothesis. Our third hypothesis was supported, since at higher wind speeds eagles flew closer to operational turbines; especially – once more – turbines in more preferred habitat. After operation, eagles effectively abandoned inner turbine locations, and flight line records close to rotor blades were rare. While our study indicated that whole-wind farm functional habitat loss through avoidance was the substantial adverse impact, we make recommendations on future wind farm design to minimise collision risk further. These largely entail developers avoiding outer turbine locations which are in and surrounded by swathes of preferred habitat. Our study illustrates the insights which detailed case studies of large raptors at wind farms can bring and emphasises that the balance between avoidance and collision can have several influences.
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Responses of dispersing GPS-tagged Golden Eagles (Aquila chrysaetos) to multiple wind farms across ScotlandWind farms may have two broad potential adverse effects on birds via antagonistic processes: displacement from the vicinity of turbines (avoidance), or death through collision with rotating turbine blades. Large raptors are often shown or presumed to be vulnerable to collision and are demographically sensitive to additional mortality, as exemplified by several studies of the Golden Eagle Aquila chrysaetos. Previous findings from Scottish Eagles, however, have suggested avoidance as the primary response. Our study used data from 59 GPS-tagged Golden Eagles with 28 284 records during natal dispersal before and after turbine operation < 1 km of 569 turbines at 80 wind farms across Scotland. We tested three hypotheses using measurements of tag records’ distance from the hub of turbine locations: (1) avoidance should be evident; (2) older birds should show less avoidance (i.e. habituate to turbines); and (3) rotor diameter should have no influence (smaller diameters are correlated with a turbine’s age, in examining possible habituation). Four generalized linear mixed models (GLMMs) were constructed with intrinsic habitat preference of a turbine location using Golden Eagle Topography (GET) model, turbine operation status (before/after), bird age and rotor diameter as fixed factors. The best GLMM was subsequently verified by k-fold cross-validation and involved only GET habitat preference and presence of an operational turbine. Eagles were eight times less likely to be within a rotor diameter’s distance of a hub location after turbine operation, and modelled displacement distance was 70 m. Our first hypothesis expecting avoidance was supported. Eagles were closer to turbine locations in preferred habitat but at greater distances after turbine operation. Results on bird age (no influence to 5+ years) rejected hypothesis 2, implying no habituation. Support for hypothesis 3 (no influence of rotor diameter) also tentatively inferred no habituation, but data indicated birds went slightly closer to longer rotor blades although not to the turbine tower. We proffer that understanding why avoidance or collision in large raptors may occur can be conceptually envisaged via variation in fear of humans as the ‘super predator’ with turbines as cues to this life-threatening agent.
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Evaluation of the Feasibility, Reliability, and Repeatability of Welfare Indicators in Free-Roaming Horses: A Pilot Study.Validated assessment protocols have been developed to quantify welfare states for intensively managed sport, pleasure, and working horses. There are few protocols for extensively managed or free-roaming populations. Here, we trialed welfare indicators to ascertain their feasibility, reliability, and repeatability using free-roaming Carneddau Mountain ponies as an example population. The project involved (1) the identification of animal and resource-based measures of welfare from both the literature and discussion with an expert group; (2) testing the feasibility and repeatability of a modified body condition score and mobility score on 34 free-roaming and conservation grazing Carneddau Mountain ponies; and (3) testing a prototype welfare assessment template comprising 12 animal-based and 6 resource-based welfare indicators, with a total of 20 questions, on 35 free-roaming Carneddau Mountain ponies to quantify inter-assessor reliability and repeatability. This pilot study revealed that many of the indicators were successfully repeatable and had good levels of inter-assessor reliability. Some of the indicators could not be verified for reliability due to low/absent occurrence. The results indicated that many animal and resource-based indicators commonly used in intensively managed equine settings could be measured in-range with minor modifications. This study is an initial step toward validating a much-needed tool for the welfare assessment of free-roaming and conservation grazing ponies.
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A Global Survey of Current Zoo Housing and Husbandry Practices for Fossa: A Preliminary ReviewThe fossa is a specialized Malagasy carnivore housed in ex situ facilities since the late 19th century. Moderate breeding success has occurred since the 1970s, and welfare issues (notably stereotypic pacing behaviour) are commonly documented. To understand challenges relating to fossa housing and husbandry (H) across global facilities and to identify areas of good practice that dovetail with available husbandry standards, a survey was distributed to ZIMS-registered zoos in 2017. Results showed that outdoor housing area and volume varied greatly across facilities, the majority of fossa expressed unnatural behaviours, with pacing behaviour the most frequently observed. All fossa received enrichment, and most had public access restricted to one or two sides of the enclosure. The majority of fossa were locked in/out as part of their daily management and forty-one percent of the fossa surveyed as breeding individuals bred at the zoo. Dense cover within an enclosure, restricted public viewing areas, a variable feeding schedule and limited view of another species from the fossa exhibit appear to reduce the risk of unnatural behavior being performed. The achievement of best practice fossa husbandry may be a challenge due to its specialized ecology, the limited wild information guiding captive care, and the range of housing dimensions and exhibit features provided by zoos that makes identification of standardized practices difficult. We recommended that holders evaluate how and when enrichment is provided and assess what they are providing for environmental complexity as well as consider how the public views their fossa.
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Evaluation of the Feasibility, Reliability, and Repeatability of Welfare Indicators in Free-Roaming Horses: A Pilot StudyValidated assessment protocols have been developed to quantify welfare states for intensively managed sport, pleasure, and working horses. There are few protocols for extensively managed or free-roaming populations. Here, we trialed welfare indicators to ascertain their feasibility, reliability, and repeatability using free-roaming Carneddau Mountain ponies as an example population. The project involved (1) the identification of animal and resource-based measures of welfare from both the literature and discussion with an expert group; (2) testing the feasibility and repeatability of a modified body condition score and mobility score on 34 free-roaming and conservation grazing Carneddau Mountain ponies; and (3) testing a prototype welfare assessment template comprising 12 animal-based and 6 resource-based welfare indicators, with a total of 20 questions, on 35 free-roaming Carneddau Mountain ponies to quantify inter-assessor reliability and repeatability. This pilot study revealed that many of the indicators were successfully repeatable and had good levels of inter-assessor reliability. Some of the indicators could not be verified for reliability due to low/absent occurrence. The results indicated that many animal and resource-based indicators commonly used in intensively managed equine settings could be measured in-range with minor modifications. This study is an initial step toward validating a much-needed tool for the welfare assessment of free-roaming and conservation grazing ponies.
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Assessing the behaviour, welfare and husbandry of mouse deer (Tragulus spp.) in European zoosMouse deer are primitive, forest ungulates found in Asia and Africa. Both the lesser mouse deer (Tragulus javanicus) and the Philippine mouse deer (T. nigricans) are managed in European zoos, but inconsistent breeding success between institutions, high neonatal mortality and a general lack of research on their husbandry and behaviour were identified by the coordinators of the European Endangered Species Programme (EEP) and the European Studbook (ESB) for each species, respectively. This study is the first to provide a behavioural description for the Philippine mouse deer and to compile a detailed behavioural repertoire for both species. Our aim was to identify the effects of current husbandry and management practices on the reproduction, behaviour and welfare of zoo-housed mouse deer. Questionnaires on husbandry and management practices were sent to all institutions in the EEP and ESB for the lesser and Philippine mouse deer, respectively, and behavioural data were collected in 15 of these zoos. For the lesser mouse deer, results show a positive effect of vegetation cover on breeding success, foraging and moving behaviours. The provision of enrichment and presence of water ponds also positively affected these behaviours. The time that pairs spent in close proximity had a negative effect on breeding success, but animals in more vegetated enclosures spent less time in close proximity to each other. Results could be partially explained by the natural habitat of this usually solitary species being tropical forest, which provides local water sources and undergrowth for cover from predators. For the Philippine mouse deer there were differences in activity measures recorded between zoos, but the sample size was small with differences in training, enrichment and vegetation cover likely to have been important. In conclusion, since mouse deer inhabit overlapping male and female territories, the usual practice of housing breeding pairs together may be appropriate, but we suggest that they should be provided with opportunities to avoid each other in complex enclosures with ample vegetation cover to maximise their natural behavioural repertoire and breeding success.
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Street-level green spaces support a key urban population of the threatened Hispaniolan Parakeet Psittacara chloropterusWhile urbanisation remains a major threat to biodiversity, urban areas can sometimes play an important role in protecting threatened species, especially exploited taxa such as parrots. The Hispaniolan Parakeet Psittacara chloropterus has been extirpated across much of Hispaniola, including from most protected areas, yet Santo Domingo (capital city of the Dominican Republic) has recently been found to support the island’s densest remaining population. In 2019, we used repeated transects and point-counts across 60 1 km2 squares of Santo Domingo to examine the distribution of parakeets, identify factors that might drive local presence and abundance, and investigate breeding ecology. Occupancy models indicate that parakeet presence was positively related to tree species richness across the city. N-Mixture models show parakeet encounter rates were correlated positively with species richness of trees and number of discrete ‘green’ patches (> 100 m2) within the survey squares. Hispaniolan Woodpecker Melanerpes striatus, the main tree-cavity-producing species on Hispaniola, occurs throughout the city, but few parakeet nests are known to involve the secondary use of its or other cavities in trees/palms. Most parakeet breeding (perhaps 50‒100 pairs) appears to occur at two colonies in old buildings, and possibly only a small proportion of the city’s 1,500+ parakeets that occupy a single roost in street trees breed in any year. Our models emphasise the importance of parks and gardens in providing feeding resources for this IUCN Vulnerable species. Hispaniola’s urban centres may be strongholds for populations of parakeets and may even represent sources for birds to recolonise formerly occupied areas on the island.
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Social Network Analysis of small social groups: application of a hurdle GLMM approach in the Alpine marmot (Marmota marmota)Social Network Analysis (SNA) has recently emerged as a fundamental tool to study animal behavior. While many studies have analyzed the relationship between environmental factors and behavior across large, complex animal populations, few have focused on species living in small groups due to limitations of the statistical methods currently employed. Some of the difficulties are often in comparing social structure across different sized groups and accounting for zero-inflation generated by analyzing small social units. Here we use a case study to highlight how Generalized Linear Mixed Models (GLMMs) and hurdle models can overcome the issues inherent to study of social network metrics of groups that are small and variable in size. We applied this approach to study aggressive behavior in the Alpine marmot (Marmota marmota) using an eight-year long dataset of behavioral interactions across 17 small family groups (7.4 ± 3.3 individuals). We analyzed the effect of individual and group-level factors on aggression, including predictors frequently inferred in species with larger groups, as the closely related yellow-bellied marmot (Marmota flaviventris). Our approach included the use of hurdle GLMMs to analyze the zero-inflated metrics that are typical of aggressive networks of small social groups. Additionally, our results confirmed previously reported effects of dominance and social status on aggression levels, thus supporting the efficacy of our approach. We found differences between males and females in terms of levels of aggression and on the roles occupied by each in agonistic networks that were not predicted in a socially monogamous species. Finally, we provide some perspectives on social network analysis as applied to small social groups to inform subsequent studies.
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The role of brain size on mammalian population densities1. The local abundance or population density of different organisms often varies widely. Understanding what determines this variation is an important, but not yet fully resolved question in ecology. Differences in population density are partly driven by variation in body size and diet among organisms. Here we propose that the size of an organism’ brain could be an additional, overlooked, driver of mammalian population densities. 2. We explore two possible contrasting mechanisms by which brain size, measured by its mass, could affect population density. First, because of the energetic demands of larger brains and their influence on life history, we predict mammals with larger relative brain masses would occur at lower population densities. Alternatively, larger brains are generally associated with a greater ability to exploit new resources, which would provide a competitive advantage leading to higher population densities among large‐brained mammals. 3. We tested these predictions using phylogenetic path analysis, modelling hypothesized direct and indirect relationships between diet, body mass, brain mass and population density for 656 non‐volant terrestrial mammalian species. We analysed all data together and separately for marsupials and the four taxonomic orders with most species in the dataset (Carnivora, Cetartiodactyla, Primates, Rodentia). 4. For all species combined, a single model was supported showing lower population density associated with larger brains, larger bodies and more specialized diets. The negative effect of brain mass was also supported for separate analyses in Primates and Carnivora. In other groups (Rodentia, Cetartiodactyla and marsupials) the relationship was less clear: supported models included a direct link from brain mass to population density but 95% confidence intervals of the path coefficients overlapped zero. 5. Results support our hypothesis that brain mass can explain variation in species’ average population density, with large‐brained species having greater area requirements, although the relationship may vary across taxonomic groups. Future research is needed to clarify whether the role of brain mass on population density varies as a function of environmental (e.g. environmental stability) and biotic conditions (e.g. level of competition).
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Contrasting responses to salinity and future ocean acidification in arctic populations of the amphipod Gammarus setosusClimate change is leading to alterations in salinity and carbonate chemistry in arctic/sub-arctic marine ecosystems. We examined three nominal populations of the circumpolar arctic/subarctic amphipod, Gammarus setosus, along a salinity gradient in the Kongsfjorden-Krossfjorden area of Svalbard. Field and laboratory experiments assessed physiological (haemolymph osmolality and gill Na+/K+-ATPase activity, NKA) and energetic responses (metabolic rates, MO2, and Cellular Energy Allocation, CEA). In the field, all populations had similar osmregulatory capacities and MO2, but lower-salinity populations had lower CEA. Reduced salinity (S = 23) and elevated pCO2 (~1000 μatm) in the laboratory for one month increased gill NKA activities and reduced CEA in all populations, but increased MO2 in the higher-salinity population. Elevated pCO2 did not interact with salinity and had no effect on NKA activities or CEA, but reduced MO2 in all populations. Reduced CEA in lower-rather than higher-salinity populations may have longer term effects on other energy demanding processes (growth and reproduction).
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The long-term impact of infant rearing background on the behavioural and physiological stress response of adult common marmosets (Callithrix jacchus)Although triplet litters are increasing in captive colonies of common marmosets, parents can rarely rear more than two infants without human intervention. There is however much evidence that early life experience, including separation from the family, can influence both vulnerability and resilience to stress. The current study investigated the behavioural and hypothalamic pituitary adrenal (HPA) axis response to the routine stressor of capture and weighing in adult common marmosets (Callithrix jacchus), reared as infants under 3 different conditions: family-reared twins (n = 6 individuals), family-reared animals from triplet litters where only 2 remain (2stays: n = 8) and triplets receiving supplementary feeding from humans (n = 7). In the supplementary feeding condition, infants remained in contact with each other when they were removed from the family. There were no significant differences (P > 0.5) in cortisol level or behaviour between the rearing conditions. In all conditions, salivary cortisol decreased from baseline to post-capture, which was accompanied by increases in agitated locomotion. Family reared 2stays demonstrated significant cortisol decreases from baseline to post capture (post 5 min.: P = 0.005; post 30 min.: P = 0.018), compared to the other conditions. Family reared twins displayed significantly more behavioural changes following the stressor than the other conditions, including significant increases in scent marking (post 5 min. and post 30 min.: P = 0.028) and significant decreases in inactive alert (post 5 min.: P = 0005; post 30 min.: P = 0.018), calm locomotion (post 5 min.: P = 0.028; post 30 min.: P = 0.046) and proximity to partner (post 5 min.: P = 0.046). There were increases in behaviour suggesting reduced anxiety, including significantly more exploration post-capture in supplementary fed triplets (post 5 min.: P = 0.041), and significantly more foraging post capture in family reared 2stays (post 5 min. and post 30 min.: P = 0.039). However, as differences between rearing conditions were minimal, supplementary feeding of large litters of marmosets at this facility did not have a major effect on stress vulnerability, suggesting that this rearing practice may be the preferred option if human intervention is necessary to improve survival of large litters.
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Effects of a no-take reserve on mangrove fish assemblages: incorporating seascape 2 connectivityNo-take reserves (NTRs) have been effective at conserving fish assemblages in tropical systems such as coral reefs, but have rarely been evaluated in turbid tropical estuaries. The present study evaluated the effect of a mangrove NTR on the conservation of juvenile fish abundance, commercial fish biomass and biodiversity at the assemblage level, and the abundance of juveniles, target and non-target adults at the family level. The evaluation incorporated one aspect of seascape connectivity, namely proximity to the sea, or in this case, the Gulf of Paria. Linear mixed models showed that the NTR had a positive effect only on species richness at the assemblage level. However, juvenile fish abundance, commercial fish biomass, taxonomic distinctness and functional diversity were not enhanced in the NTR. The inclusion of connectivity in these models still failed to identify any positive effects of the NTR at the assemblage level. Yet, there were significant benefits to juvenile fish abundance for 5 of 7 families, and for 1 family of non-target adults. Possible explanations for the limited success of the NTR for fish assemblages include failing to account for the ecology of fish species in NTR design, the drawbacks of ‘inside−outside’ (of the NTR) experimental designs and the fact that fishing does not always impact non-target species. It is important to recognise that mangrove NTRs do not necessarily benefit fish assemblages as a whole, but that finer-scale assessments of specific families may reveal some of the proclaimed benefits of NTRs in tropical estuaries.
