Captive Breeding Research Articles

Reproductive Behavior and Parental Role of Giant Gourami (<i>Osphronemus goramy</i> Lacepède, 1801)

The giant gourami (Osphronemus goramy Lacepede, 1801), a popular aquaculture species in Southeast Asia, exhibits unique cooperative biparental care behaviour. To support captive breeding efforts, this study aimed to visually document the reproductive activity of giant gourami, elucidate each stage in detail, and provide insights into the distinct parenting roles of males and females. Underwater cameras were used to observe a breeding pair of gourami in a pond for five days, conducted three times with different pairs during different spawning periods. The male and female contributions to nest building were quantitatively analysed using the T-test, while their parental care involvement was qualitatively assessed and statistically analysed using the Mann-Whitney U test. The results revealed three main phases of giant gourami reproduction: pre-spawning (including adaptation, nest building, and courtship), spawning and fertilisation, and post-spawning with parental care. Our observation confirmed the biparental tendency, with males being more involved in pre-spawning activities and females taking on a prominent role in post-spawning care. In conclusion, males focused on mating preparations and courtship, while females invested more in parental care.

Identifying personality traits and behavioural syndromes in a threatened freshwater fish (Nannoperca vittata) through comparative analysis with a model species (Poecilia reticulata): Implications for conservation

AbstractAnimal personalities are differences in behaviour among individuals of the same species that are consistent over time and contexts. The integration of animal personality into conservation actions is hampered by limited understanding of personality traits in non‐model organisms. We estimated repeatabilities and correlations between behaviours in Nannoperca vittata (western pygmy perch), a threatened freshwater fish species endemic to south‐western Australia, and, for comparative purposes, in Poecilia reticulata (guppy), a species frequently used in personality research. Each fish was measured four times for each of seven behavioural variables, presumed to reflect five underlying personality traits. Track length (TL) was used as a measure of activity; time spent in a risky zone (RZ) and time to emergence (ET) for boldness; latency to approach a novel object (LA) and time spent close to the object (TS) for exploration; time spent close to a mirror (CV) for sociability and number of attacks at the mirror (AT) for aggression. Four behavioural variables (TL, RZ, ET and CV) were significantly repeatable in N. vittata and also in P. reticulata. There was a lack of concordance in phenotypic and among‐individual correlations between variables in both species, emphasising the importance of partitioning trait covariances to infer behavioural syndromes. Significant among‐individual correlations were found between activity, boldness and sociability variables in N. vittata, consistent with a proactive‐reactive personality axis, but not in P. reticulata. Personality variation should be considered in conservation actions for N. vittata, particularly with respect to unintended consequences of domestication selection in captive breeding and release.

Optimizing Goldfish (Carassius auratus) Breeding and Larval Nurturing for Materialistic Aquaculture Utilizing Synthetic Hormones

Gold fish (Carassius auratus) are familiar in India as an ornamental freshwater fish with economic importance. This experiment aimed to explore the possibility for mass-scale breeding and larval rearing of goldfish under biofloc setup. Natural brooders were collected, acclimatized and induced to breed utilizing synthetic hormones at various dosages. Breeding execution parameters namely spawning success, fertilization rate and hatching performance were analysed. The highest fertilization and hatching rate were gradually noticed at 80.8% and 80.9% by using a dose of 0.4ml/kg body weight for females and 0.2ml/kg for males. Larval rearing was accomplish by applying several live and formulated feeds across various life stages in normal rearing tanks and biofloc tanks also. The growth performance of larvae in biofloc tanks express a satisfactory rate, with a maximum weight gain of 7.1 g and length gain of 5 cm over 120 days compared to 5.1 g and 3.5 cm in normal tanks. Water quality parameters were kept within the optimum range all over the experiment. The functionable study exhibits the viability of captive breeding and mass scale larval nurturing of goldfish employing induced breeding techniques and biofloc technology.

First Feeding of Cuttlefish Hatchlings: Pioneering Attempts in Captive Breeding.

In the last few decades, the cuttlefish market has grown to approximately 14% of the world's fisheries, and operators have begun to express concerns about the decline of this resource. In this context, the production of cuttlefish through aquaculture could offer a diversifying and valuable response to the increasing market demand and help alleviate the environmental pressure on this species. Therefore, the aim of this study is to identify a dry, cost-effective, and easy-to-administer diet that can successfully support the initial phases of cuttlefish growth and provide a similar performance to a krill-based diet, which closely mimics their natural diet. To achieve this objective, cuttlefish hatchlings were distributed among different experimental tanks, each receiving one of the five different diets (namely Diets A to E). Mortality and morphological parameters were monitored until day 10 post hatching, and the two most effective diets (Diets A and B) were chosen for further trials. The results indicated that Diet B had similar survival and growth rates to Diet A, which was based on frozen krill. Histological analysis revealed a comparable degree of gut maturity between the organisms fed the two diets. Likewise, levels of amylase and trypsin enzymes and hsp70, cat, and sod mRNA did not exhibit significant differences between the two groups. In conclusion, our findings provide preliminary evidence supporting the possibility of cultivating cuttlefish in captivity using a pelleted diet, representing a promising starting point for larger-scale breeding efforts.

Drivers of genomic diversity and phenotypic development in early phases of domestication in Hermetia illucens.

The black soldier fly (BSF), Hermetia illucens, has the ability to efficiently bioremediate organic waste into usable bio-compounds. Understanding the impact of domestication and mass rearing on fitness and production traits is therefore important for sustainable production. This study aimed to assess patterns of genomic diversity and its association to phenotypic development across early generations of mass rearing under two selection strategies: selection for greater larval mass (SEL lines) and no direct artificial selection (NS lines). Genome-wide single nucleotide polymorphism (SNP) data were generated using 2bRAD sequencing, while phenotypic traits relating to production and population fitness were measured. Declining patterns of genomic diversity were observed across three generations of captive breeding, with the lowest diversity recorded for the F3 generation of both selection lines, most likely due to founder effects. The SEL cohort displayed statistically significantly greater larval weight com the NS lines with pronounced genetic and phenotypic directional changes across generations. Furthermore, lower genetic and phenotypic diversity, particularly for fitness traits, were evident for SEL lines, illustrating the trade-off between selecting for mass and the resulting decline in population fitness. SNP-based heritability was significant for growth, but was low or non-significant for fitness traits. Genotype-phenotype correlations were observed for traits, but individual locus effect sizes where small and very few of these loci demonstrated a signature for selection. Pronounced genetic drift, due to small effective population sizes, is likely overshadowing the impacts of selection on genomic diversity and consequently phenotypic development. The results hold particular relevance for genetic management and selective breeding for BSF in future.

First success in captive breeding of the Tiger Cowrie, Cypraea tigris (Gastropoda: Cypraeidae), with notes on its early life development

ABSTRACT The larval development of cowries has remained underexplored due to challenges associated with restricted growth and high mortalities, and as a result, their larvae never achieve competency or metamorphosis. In this study, we conducted a series of experiments using Cypraea tigris larvae to optimise the culture protocols. Broadly, there were no apparent differences in larval survival rates among the seawater quality levels (0.2, 1 aged, 50 μm filtered seawater). In contrast, a microalgal diet solely of Tisochrysis lutea and a mixed diet of Rhodomonas salina + Chaetoceros mulleri had higher larval survival rates than two other mixed diets (i.e., T. lutea + Tetraselmis suecica and T. suecica + R. salina). The provision of 10 ppm of the antibiotic streptomycin sulphate also boosted larval survival by preventing ciliate infection and minimising bacterial growth. We subsequently improved culture protocols by applying new information from these experiments and report the first successful captive breeding of C. tigris through to settlement. The C. tigris larvae reared at 28°C attained competency as early as 40 days post-hatching and metamorphosed by 42 days upon transfer to a well-conditioned tank. Observations of C. tigris larvae and early-stage juvenile development were documented for the first time and are reported herein.

ADULT LONGEVITY OF Idea blanchardii (LEPIDOPTERA: NYMPHALIDAE) CAPTIVE BRED AT LIPI BUTTERFLY BREEDING FACILITY, CIBINONG, INDONESIA

Idea blanchardii is one of many endemic butterfly species in Sulawesi, Indonesia. This species is among the highly traded butterfly species thus requires biological information on the captive breeding. The aim of this study was to obtain data on the adult life-span, to report the multivoltine generation, and to provide conservation-related insight. Captive breeding research on this species was conducted within the period of September 2018 until February 2020. The host plant, Parsonsia alboflavescens, was used to support the life of this species for ovipositing and larval food plant. The adults would visit almost any flowers available at the facility. In total, 696 individuals were observed. Data on mating information of the species is presented here. Observations on when a female lays eggs are also revealed. This research showed that I. blanchardii is polygamous and polyandrous. Individuals of this species could live much longer than other butterfly species. A few could live over 80 days and one still seen laying eggs at the age of 136 days old.

Competitive interactions affect introgression and population viability amidst maladaptive hybridization.

The deliberate release of captive-bred individuals, the accidental escape of domesticated strains, or the invasion of closely related conspecifics into wild populations can all lead to introgressive hybridization, which poses a challenge for conservation and wildlife management. Rates of introgression and the magnitude of associated demographic impacts vary widely across ecological contexts. However, the reasons for this variation remain poorly understood. One rarely considered phenomenon in this context is soft selection, wherein relative trait values determine success in intraspecific competition for a limiting resource. Here we develop an eco-genetic model explicitly focussed on understanding the influence of such competitive interactions on the eco-evolutionary dynamics of wild populations experiencing an influx of foreign/domesticated individuals. The model is applicable to any taxon that experiences natural or human-mediated inputs of locally maladapted genotypes ('intrusion'), in addition to phenotype-dependent competition for a limiting resource (e.g. breeding sites, feeding territories). The effects of both acute and chronic intrusion depended strongly on the relative competitiveness of intruders versus locals. When intruders were competitively inferior, density-dependent regulation limited their reproductive success (ability to compete for limited spawning sites), which prevented strong introgression or population declines from occurring. In contrast, when intruders were competitively superior, this amplified introgression and led to increased maladaptation of the admixed population. This had negative consequences for population size and population viability. The results were sensitive to the intrusion level, the magnitude of reproductive excess, trait heritability and the extent to which intruders were maladapted relative to locals. Our findings draw attention to under-appreciated interactions between phenotype-dependent competitive interactions and maladaptive hybridization, which may be critical to determining the impact captive breeding programmes and domesticated escapees can have on otherwise self-sustaining wild populations.

Can sustainable biocommerce continue to support conservation, or will the captive breeding of offspring be its Achilles heel?

Abstract The trade in high‐value natural resources, particularly exotic plants and animals (henceforth biocommerce), can lead to both positive and negative impacts on wild populations. The exotic plant and animal hobbies are highly organized with internal cultures that are often poorly understood by non‐members; however, understanding them is of central importance for biocommerce with both direct and indirect consequences for the conservation of wild populations. Growing international demands for exotic species leaves simple questions related to the economics of biocommerce unexplored. The long‐term success of biocommerce businesses requires constant income, meaning they obtain and retain significant market proportions. Some biocommerce products can be reproduced by hobbyists and undercut business efforts based on sustainably produced exports. We analyse a test case in Neotropical poison frogs where sustainable biocommerce is burgeoning, yet (export‐based) businesses face direct market competition from the offspring produced within the countries, which receive their exports, and therefore are forced to rely on fervent customer support. Solution: We survey customers' behaviours where we find different classes of consumers, which differ in where they place higher values within the hobby. By taking into account these different classes, we gain insights and potential solutions to promote the stability of this unique type of biocommerce.

Inconsistent reproductive cycles and postnatal growth between captive and wild Chinese pangolins and its conservation implications

Captive breeding and reintroduction are crucial to the conservation of endangered species and restoring their populations in the wild. Previous research has primarily focused on behavioral changes and adaptations in captive-bred animals prior to release; few studies have examined changes in reproductive traits and postnatal development in captivity. The Chinese pangolin, Manis pentadactyla, is Critically Endangered because its population has substantially declined in the wild due to poaching for sale in the traditional medicine and luxury food markets. Nevertheless, success in captive breeding in Taiwan may provide a pathway to the recovery of wild populations. This study combined records on captive individuals and field observations on wild Chinese pangolins over a period from 1997 to 2023 to determine (i) mating season, (ii) birth timing, (iii) body mass and total length of newborns, and (iv) postnatal growth patterns prior to weaning. The present study suggests that mating and birth timings for captive Chinese pangolins are not seasonal, as they are in the wild. Captive-born infants are significantly longer and heavier at birth than wild-born infants. Remarkably, captive-born pangolins also experience more rapid weight gain, nearly doubling in size compared with their wild counterparts by 25 weeks of age, even before they are weaned. This rapid growth is likely attributable to the high nutritional content of captive diets. This study suggests artificial feed formulas should be aligned more closely with wild pangolins’ diets to reduce the risk of obesity. Additionally, reproductive parameters and postnatal growth rates in Chinese pangolins cannot be based on observations of captive individuals alone; wild populations must also be considered. We conclude that Chinese pangolins exhibit physiological flexibility in reproduction and growth in response to environmental changes, providing insights for captive pangolin management and reintroduction programs.

Current social management practices contribute to reproductive failure in zoo-housed guenons

Recent emphasis on reflecting natural behaviour and wild group composition in zoo-housed social animals has resulted in substantial improvement in captive breeding and welfare. We investigated studbook data for four guenon species housed in European zoos to assess the role of zoo management practices in the reproductive success of social species. We hypothesized that group dynamics reflecting wild living, including early social experience, would be associated with greater reproductive success. Our findings are presented in a standardized qualitative risk assessment with an additional certainty measure in the form of literature evidence. We found that greater reproductive success was associated with more potential breeding partners in L’Hoest’s, Roloway and Diana monkeys and with larger group sizes in all species studied here, providing support that mimicking wild group size, composition, and dynamics under captive conditions can improve reproductive success. Unexpectedly, greater reproductive success was associated with earlier first inter-facility transfers in female L’Hoest’s and Diana monkeys, and with more frequent inter-facility transfers in male L’Hoest’s and Diana monkeys. Furthermore, for male Diana monkeys and female and male L’Hoest’s monkeys, mothers with less reproductive and rearing experience tended to produce offspring that in turn had greater reproductive success, hinting at more complex and sex-differentiated mechanisms underlying sub-optimal reproduction in zoo guenons. Our findings highlight the importance of carrying out species-specific studies, and demonstrate that zoo management and husbandry practices can inadvertently impact reproductive success. We recommend that zoos holding guenons consider reducing the number of guenon species they hold in favour of increasing group size to improve reproductive success.

Thirty years of conservation breeding: Assessing the genetic diversity of captive Livingstone's fruit bats.

Fruit bats (genus Pteropus) are typically island-endemic species important in seed dispersal and reforestation that are vulnerable to increased extinction risk. An effective method of reducing extinction risk in vulnerable species that cannot be conserved in their native habitat is establishing an ex-situ captive breeding programme. Due to anthropogenic threats and low population numbers, in the early 1990s, a captive breeding programme was established at Jersey Zoo, British Isles, for Critically Endangered Livingstone's fruit bats (Pteropus livingstonii). Here we use six polymorphic microsatellite loci to assess genetic diversity in the captive breeding population of Livingstone's fruit bats (P. livingstonii), 30 years after the programme's establishment, investigating change over generations and comparing our findings with published data from the wild population. We found no significant difference between the genetic diversity in the captive and wild populations of Livingstone's fruit bats (P. livingstonii), in both expected heterozygosity and allelic richness. The captive population has retained a comparable level of genetic diversity to that documented in the wild, and there has been no significant decline in genetic diversity over the last 30 years. We advise that a full pedigree of the paternal lineage is created to improve the management of the captive breeding programme and further reduce the possibility of inbreeding. However, it appears that the captive breeding programme is currently effective at maintaining genetic diversity at levels comparable to those seen in the wild population, which suggests reintroductions could be viable if genetic diversity remains stable in captivity.

Evidence of dystocia in an oviparous shark.

Dystocia, or obstructed labor, is a well-documented phenomenon in various captive vertebrates, including fish. However, despite the documentation of dystocia in several viviparous (live-bearing) Chondrichthyan species (i.e., sharks, rays, skates, and chimaeras), there are no reports to date of dystocia in any oviparous (egg-laying) species. Here we present a case of a captive female epauletteshark (Hemiscyllium ocellatum) that demonstrated symptoms of dystocia in a research-related captive breeding programme. This communication serves as documentation that dystocia can occur in oviparous Chondrichthyans, and this information can help inform researchers and veterinary practitioners for improved care.

RETROSPECTIVE STUDY OF MORBIDITY AND MORTALITY IN A CAPTIVE POPULATION OF CRYPTOSPORIDIUM-POSITIVE LOUISIANA PINE SNAKES (PITUOPHIS RUTHVENI).

The Louisiana pine snake (Pituophis ruthveni) is a diurnal colubrid species native to Louisiana and eastern Texas whose free-ranging populations have been declining over at least the past 30 yr. The creation and maintenance of sustainable captive breeding programs of P. ruthveni to restore native populations has also provided ample opportunity for research into this species and for P. ruthveni to serve as a research model for other colubrid snakes. However, no investigation into prevalent causes of morbidity and mortality in captive populations of this species has been described. A research population of P. ruthveni was maintained at Louisiana State University (LSU) for over 4 yr due to unsuitability for breeding after testing positive for Cryptosporidium serpentis. Since arrival at LSU, the snakes were under close veterinary surveillance. Complete postmortem examinations were performed on 12 snakes that died or were euthanized. The aim of this study was to further understanding of common factors influencing morbidity and mortality in captive P. ruthveni infected with C. serpentis, by retrospectively reviewing postmortem exam findings from the 12 deceased members of the population at LSU. A predominant finding across individuals included bacterial infections, which were responsible for major illness or death in 37.5% of the animals. Fifty percent of snakes tested positive for Cryptosporidium sp. based on PCR performed from postmortem samples; it was directly implicated as cause of death or morbidity in 83.3% of positive cases. Although infectious disease represented the most common pathologic postmortem finding, several noninfectious disease processes were identified, including gout, goiter, and neoplasia. These findings mirror those of other retrospective investigations of reptile collections at various institutions and highlight the need for appropriate emphasis on the identification, treatment, and prevention of infectious disease as part of routine veterinary care.

Genetic assessment of eight zoo populations of golden snub-nosed monkey (Rhinopithecus roxellana) implication to the conservation management of captive populations.

Captive breeding programs play an important role in preserving the genetic diversity of endangered species. It is of utmost importance to conduct genetic assessment for captive populations in order to develop scientific breeding plans and conservation management strategies. Here, we genotyped 10 microsatellite loci and sequenced 368 bp of mitochondrial DNA control region for the golden snub-nosed monkey (Rhinopithecus roxellana) from eight captive populations in China, and compared the genetic indices of captive populations with a wild population. Meanwhile, we performed paternity tests to verify the genealogical records and established genetic lineages. A total of 157 individuals were identified from 161 fecal samples, including 135 captive individuals (approximately 25% of captive individuals in China). Microsatellite analysis showed that the nine populations had moderate levels of genetic diversity, with polymorphism information content (PIC) ranging from 0.43 to 0.542; the genetic diversity of captive populations (average PIC: 0.503) was slightly higher than that of the wild population (PIC: 0.438). The Structure analysis indicated that individuals of the eight captive populations contained two different genetic components. We conducted either single-blind or double-blind paternity testing on 40 offspring of captive individuals and found that five offspring from two zoos (Nanjing Hongshan Forest Zoo and Shanghai Wild Animal Park) showed discrepant kinships from their pedigree records, probably due to the inaccuracies in pedigree records. By constructing genetic pedigrees, inbred offspring were found in Beijing Zoo, Shanghai Zoo, Hangzhou Zoo, and Chengdu Zoo. Analysis based on mitochondrial DNA showed a high level of genetic diversity in the eight captive populations (mean nucleotide diversity: 0.047). However, no nucleotide diversity was found in the wild population. This study conducted a genetic survey for captive golden snub-nosed monkeys and will significantly benefit the genetic conservation management for captive populations in the future.

Distinct Island Lineages of Binturong (Arctictis binturong) from Indonesia and Its Conservation Implications

Binturong (Arctictis binturong) is a threatened carnivore that inhabits the forests of South and Southeast Asia. Despite its wide range, binturong is relatively scarce across its habitat distribution and is currently under the threat of poaching and illegal trade. Captive breeding has unfortunately been conducted rather haphazardly with a lack of origin record maintained, implicating potential risks to the management such as inbreeding or genetic swamping. This study thus aims to characterise the phylogenetic relationship of Indonesian binturong within the context of Southeast Asian binturong and further probe the distinctness of lineages originating from Java, Sumatra, Indonesian Borneo, and Bangka using Cytochrome B (CytB) and Cytochrome C Oxidase Subunit 1 (CO1). Genetic distance, phylogram topology, and haplotype analysis of both encoding genes further corroborate the distinctness of Java, Borneo, and Bangka binturong from other binturong from Indochinese regions such as India, Laos, and Myanmar. Search for prospective single nucleotide polymorphism markers to discriminate island lineages consistently found that each Java, Bangka, and Bornean binturong be distinct from each other and other lineages, especially when assessed using haplotype-based clustering. Assigning binturong originated from Sumatra is nonetheless more complicated, suggesting the possibility. Our findings substantiated the much-needed systematic research of Southeast Asian binturong as ex-situ insurance population management grows in Indonesia and other parts of the world to protect the diversity of binturong lineages and their corresponding unique evolutionary history.

The genome of Przewalski's horse (Equus ferus przewalskii).

The Przewalski's horse (Equus ferus przewalskii) is an endangered equid native to the steppes of central Asia. After becoming extinct in the wild multiple conservation efforts convened to preserve the species, including captive breeding programs, reintroduction and monitoring systems, protected lands, and cloning. Availability of a highly contiguous reference genome is essential to support these continued efforts. We used Oxford Nanopore sequencing to produce a scaffold-level 2.5 Gb nuclear assembly and 16,002 bp mitogenome from a captive Przewalski's mare. All assembly drafts were generated from 111 Gb of sequence from a single PromethION R10.4.1 flow cell. The mitogenome contained 37 genes in the standard mammalian configuration and was 99.63% identical to the domestic horse (Equus caballus). The nuclear assembly, EquPr2, contained 2,146 scaffolds with an N50 of 85.1 Mb, 43X mean depth, and BUSCO quality score of 98.92%. EquPr2 successfully improves upon the existing Przewalski's horse reference genome (Burgud), with 25-fold fewer scaffolds, a 166-fold larger N50, and phased pseudohaplotypes. Modified basecalls revealed 79.5% DNA methylation and 2.1% hydroxymethylation globally. Allele-specific methylation analysis between pseudohaplotypes revealed 226 differentially methylated regions in known imprinted genes and loci not previously reported as imprinted. The heterozygosity rate of 0.165% matches previous estimates for the species and compares favorably to other endangered animals. This improved Przewalski's horse assembly will serve as a valuable resource for conservation efforts and comparative genomics investigations.

Genome of the endangered eastern quoll (Dasyurus viverrinus) reveals signatures of historical decline and pelage color evolution

The eastern quoll (Dasyurus viverrinus) is an endangered marsupial native to Australia. Since the extirpation of its mainland populations in the 20th century, wild eastern quolls have been restricted to two islands at the southern end of their historical range. Eastern quolls are the subject of captive breeding programs and attempts have been made to re-establish a population in mainland Australia. However, few resources currently exist to guide the genetic management of this species. Here, we generated a reference genome for the eastern quoll with gene annotations supported by multi-tissue transcriptomes. Our assembly is among the most complete marsupial genomes currently available. Using this assembly, we infer the species’ demographic history, identifying potential evidence of a long-term decline beginning in the late Pleistocene. Finally, we identify a deletion at the ASIP locus that likely underpins pelage color differences between the eastern quoll and the closely related Tasmanian devil (Sarcophilus harrisii).

In Absentia—Can a Lack of Behaviour Be a Useful Welfare Indicator? An Application to the Captive Management of Livingstone’s Fruit Bats, Pteropus livingstonii

Non-invasive behavioural indicators of welfare can be particularly useful for managing captive breeding populations of endangered species; these allow individual welfare to be monitored and reproductive success maximised without the need for capture and restraint methods. However, most studies focus on the behaviours whose presence or frequency can predict welfare issues; the absence of a behaviour is less frequently considered an indicator of welfare. Here, we investigate potential behavioural correlates with welfare-related health states in captive Livingstone’s fruit bats (Pteropus livingstonii), a critically endangered species that can become obese due to restricted space and reduced activity rates compared with wild populations. In this study, behavioural data were collected on males (which are particularly prone to obesity). Hurdle models were used to separately determine the factors predicting the presence or absence of behaviour and the frequency of observed behaviours. Whilst significantly lower levels of vigilance were observed in males with a larger body mass, those with diagnosed health issues were significantly more likely to show an absence of locomotion and foraging behaviour. Males with a lower body mass were also more likely to show an absence of foraging behaviour. Our study demonstrates how the absence of a behaviour can be informative as to an individual’s welfare state. This study has identified behavioural profiles that can be used to flag at-risk individuals, reducing the need for potentially stressful handling and improving our ability to safeguard the welfare of individuals within a large captive group.

Quantifying intraspecific variation in host resistance and tolerance to a lethal pathogen.

Testing for intraspecific variation for host tolerance or resistance in wild populations is important for informing conservation decisions about captive breeding, translocation, and disease treatment. Here, we test the importance of tolerance and resistance in multiple populations of boreal toads (Anaxyrus boreas boreas) against Batrachochytrium dendrobatidis (Bd), the amphibian fungal pathogen responsible for the greatest host biodiversity loss due to disease. Boreal toads have severely declined in Colorado (CO) due to Bd, but toad populations challenged with Bd in western Wyoming (WY) appear to be less affected. We used a common garden infection experiment to expose post-metamorphic toads sourced from four populations (2 in CO and 2 in WY) to Bd and monitored changes in mass, pathogen burden and survival for 8 weeks. We used a multi-state modelling approach to estimate weekly survival and transition probabilities between infected and cleared states, reflecting a dynamic infection process that traditional approaches fail to capture. We found that WY boreal toads are more tolerant to Bd infection with higher survival probabilities than those in CO when infected with identical pathogen burdens. WY toads also appeared more resistant to Bd with a higher probability of infection clearance and an average of 5 days longer to reach peak infection burdens. Our results demonstrate strong intraspecific differences in tolerance and resistance that likely contribute to why population declines vary regionally across this species. Our multi-state framework allowed us to gain inference on typically hidden disease processes when testing for host tolerance or resistance. Our findings demonstrate that describing an entire host species as 'tolerant' or 'resistant' (or lack thereof) is unwise without testing for intraspecific variation.