Conserving avian vocal culture

Over 40% of bird species learn their vocalizations from conspecifics. Avian vocalizations therefore represent one of the most pervasive and quantifiable examples of culturally acquired behaviour that evolves and is maintained within populations through conformity and selection. We review research exploring the loss of vocal culture in wild birds and synthesize how this loss may occur through three processes, defined as erosion/fragmentation, divergence and convergence. We discuss the potential to conserve avian vocal cultures in the wild and in captivity, using the regent honeyeater Anthochaera phrygia as a case study. Given the current rates of global biodiversity decline, we predict that more examples of avian vocal culture loss will emerge in the future. There is a need, therefore, for a better understanding of (i) how pervasive loss of vocal culture is in birds; (ii) what factors predispose birds to loss of vocal culture; (iii) the fitness costs of loss of vocal culture, including the population size or density range within which fitness costs may be greatest; and (iv) how vocal cultures can best be conserved or restored. This knowledge could then inform management actions such that the diversity of the world's birds and their vocalizations can be maintained for generations to come.This article is part of the theme issue 'Animal culture: conservation in a changing world'.

The flexibility of social learning and its conservation implications in mammals and beyond

Conservation strategies seek to ensure that populations persist and are resilient to environmental change. As learning from others can shape the development of skills that help animals survive, reproduce and respond to changing conditions, understanding social learning can be of crucial conservation importance. Research on mammals, with their great diversity of niches and social systems, provides vital evidence that social learning helps animals to communicate, secure mates, avoid predators, forage effectively and navigate through their ecological and social environments. However, these environments are being rapidly altered in the Anthropocene, influencing individuals' reliance on social learning, the value of learned information, its spread through groups and the stability of socially learned traditions. Here, we review and synthesize this growing body of literature to highlight how understanding the ways in which animals use social learning and deploy it flexibly throughout their lives may enhance conservation programmes. We consider both the potential negative consequences of social learning and the scope for social-learning-driven interventions to generate adaptive responses to the challenges of rapidly changing environments. A greater appreciation and integration of social learning and its flexibility will ultimately promote the effective conservation of mammals and other taxa in our fast-changing world.This article is part of the theme issue 'Animal culture: conservation in a changing world'.

Temporal Loss of Genome-Wide and Immunogenetic Diversity in a Near-Extinct Parrot

Loss of genetic diversity threatens a species' adaptive potential and long-term resilience. Predicted to be extinct by 2038, the orange-bellied parrot (Neophema chrysogaster) is a critically endangered migratory bird threatened by numerous viral, bacterial and fungal diseases. The species has undergone multiple population crashes, reaching a low of three wild-born females and 13 males in 2016, and is now represented by only a single wild population and individuals in the captive breeding program. Here we used our high-quality long-read reference genome, and contemporary (N = 19) and historical (N = 16) resequenced genomes from as early as 1829, to track the long-term genomic erosion and immunogenetic diversity decline in this species. 62% of genomic diversity was lost between historical (mean autosomal heterozygosity = 0.00149 ± 0.000699 SD) and contemporary (0.00057 ± 0.000026) parrots. A greater number and length of runs of homozygosity in contemporary samples were also observed. A temporal reduction in the number of alleles at Toll-like receptor genes was found (historical average alleles = 5.78 ± 2.73; contemporary = 3.89 ± 2.10), potentially exacerbating disease susceptibility in the contemporary population. Of particular concern is the new threat of avian influenza strain (HPAI) to Australia. We discuss the conservation implications of our findings and propose that hybridisation and synthetic biology may be required to address the catastrophic loss of genetic diversity that has occurred in this species in order to prevent extinction.

Strategies for integrating animal social learning and culture into conservation translocation practice

Conservation translocations are increasingly used in species' recovery. Their success often depends upon maintaining or restoring survival-relevant behaviour, which is socially learned in many animals. A lack of species- or population-appropriate learning can lead to the loss of adaptive behaviour, increasing the likelihood of negative human interactions and compromising animals' ability to migrate, exploit resources, avoid predators, integrate into wild populations, reproduce and survive. When applied well, behavioural tools can address deficiencies in socially learned behaviours and boost survival. However, their use has been uneven between species and translocation programmes, and behaviour commonly contributes to translocation failure. Critically, current international guidance (e.g. the International Union for Conservation of Nature's translocation guidelines) does not directly discuss social learning or its facilitation. We argue that linking knowledge about social learning to appropriate translocation strategies will enhance guidance and direct future research. We offer a framework for incorporating animal social learning into translocation planning, implementation, monitoring and evaluation across wild and captive settings. Our recommendations consider barriers practitioners face in contending with logistics, time constraints and intervention cost. We emphasize that stronger links between researchers, translocation practitioners and wildlife agencies would increase support for social learning research, and improve the perceived relevance and feasibility of facilitating social learning.This article is part of the theme issue 'Animal culture: conservation in a changing world'.

Captivity Reduces Diversity and Shifts Composition of the Great Bustard (Otis tarda dybowskii) Microbiome

Captivity offers protection for endangered species, but for bustards, captive individuals face a higher risk of disease and exhibit lower reintroduction success rates. Changes in the diversity of host bacterial and fungal microbiota may be a significant factor influencing reintroduction success. The great bustard (Otis tarda) is a globally recognized endangered bird species. Previous research on the gut microbiota of the great bustard has been limited, hindering effective conservation efforts. Therefore, this study utilized high-throughput sequencing of the 16S rRNA and Internal Transcribed Spacer (ITS) genes to compare the gut bacterial and fungal microbiota of great bustards in different environments. The results revealed a significant decline in alpha diversity and notable changes in microbial community structure in captive environments. Changes in diet and habitat are likely major factors contributing to these shifts. Consequently, managing rescued wild animals by increasing dietary diversity and exposure to natural environmental reservoirs may enhance the success rate of reintroduction efforts.

Nest quality predicts the probability of egg loss in the critically endangered 'Alalā (Corvus hawaiiensis)

Conservation breeding programs for endangered species face challenges, notably in the development of husbandry techniques, complicated by the impracticality of conducting controlled experiments. To reduce uncertainty regarding what works in conservation breeding programs, it is essential to capture data. In avian breeding programs, the construction of quality nests and appropriate incubation and handling of eggs by the parents are essential prerequisites to the successful production of offspring. Here, we study factors influencing nest-building and parental incubation outcomes in 'alalā (Corvus hawaiiensis), which is extinct in the wild and numbers fewer than 130 individuals in human care. Using parent-incubated egg data from 2018 to 2021 (171 clutches, 55 pairs), we evaluated the role of husbandry factors in determining the quality of nests constructed by 'alalā and the likelihood of nest quality and other social and environmental factors to predict egg loss (breaking, cannibalization, or ejection of an egg from the nest). More than half of all eggs laid failed to reach the hatch date. Nest quality was the most influential predictor of egg loss, with eggs in higher quality nests more likely to reach the hatch date. Male age also influenced egg loss, with very young (3 years old) and older males (⪞12 years old) experiencing more egg loss. Furthermore, the two facilities and two aviary types also differed in the quality of nests 'alalā constructed, indicating that nest-building behavior can be influenced by husbandry practices. These findings reduce uncertainty and provide insights for recommended management interventions to facilitate successful reproduction in human care.

Adapting conservation breeding techniques using a data-driven approach to restore the 'Alalā (Hawaiian crow, Corvus hawaiiensis)

For some critically endangered species, conservation breeding is a vital steppingstone toward re-establishing wild populations. The 'Alalā (Hawaiian crow, Corvus hawaiiensis), currently extinct in the wild, exists today only in a conservation breeding program, which, for many years, utilized successful hands-on husbandry approaches such as separating and resocializing pairs, providing partially manmade nests, artificially incubating eggs, and puppet rearing nestlings. Yet, a top priority of any conservation breeding program is to retain natural behaviors essential to postrelease survival and reproduction, to achieve successful reintroduction and restoration to the wild. We describe how we are adapting 'Alalā husbandry techniques to strengthen pair bonds through full-time socialization, enable pairs to build robust nests, encourage females to incubate eggs to hatch, and provide pairs and their offspring with vital parental rearing experiences. We discuss the use of standardized, data-driven methods to objectively track our progress towards successful parental breeding and to select release candidates based on their likelihood to survive and breed in the wild. The information shared in this report can be applied to other conservation breeding programs, particularly those implementing or transitioning to husbandry techniques geared towards preparing species to thrive in the wild.

The endangered brain: actively preserving ex-situ animal behaviour and cognition will benefit in-situ conservation

Endangered species have small, unsustainable population sizes that are geographically or genetically restricted. Ex-situ conservation programmes are therefore faced with the challenge of breeding sufficiently sized, genetically diverse populations earmarked for reintroduction that have the behavioural skills to survive and breed in the wild. Yet, maintaining historically beneficial behaviours may be insufficient, as research continues to suggest that certain cognitive-behavioural skills and flexibility are necessary to cope with human-induced rapid environmental change (HIREC). This paper begins by reviewing interdisciplinary studies on the 'captivity effect' in laboratory, farmed, domesticated and feral vertebrates and finds that captivity imposes rapid yet often reversible changes to the brain, cognition and behaviour. However, research on this effect in ex-situ conservation sites is lacking. This paper reveals an apparent mismatch between ex-situ enrichment aims and the cognitive-behavioural skills possessed by animals currently coping with HIREC. After synthesizing literature across neuroscience, behavioural biology, comparative cognition and field conservation, it seems that ex-situ endangered species deemed for reintroduction may have better chances of coping with HIREC if their natural cognition and behavioural repertoires are actively preserved. Evaluating the effects of environmental challenges rather than captivity per se is recommended, in addition to using targeted cognitive enrichment.

The phenotypic costs of captivity

The breeding of threatened species in captivity for release is a central tool in conservation biology. Given gloomy predictions for biodiversity trends in the Anthropocene, captive breeding will play an increasingly important role in preventing future extinctions. Relative to the wild, captive environments drastically alter selection pressures on animals. Phenotypic change in captive animals in response to these altered selection pressures can incur fitness costs post-release, jeopardising their potential contribution to population recovery. We explore the ways in which captive environments can hinder the expression of wild phenotypes. We also stress that the phenotypes of captive-bred animals differ from their wild counterparts in multiple ways that remain poorly understood. We propose five new research questions relating to the impact of captive phenotypes on reintroduction biology. With better use of monitoring and experimental reintroductions, a more robust evidence base should help inform adaptive management and minimise the phenotypic costs of captivity, improving the success of animal reintroductions.

Altered wing phenotypes of captive-bred migratory birds lower post-release fitness

Captive breeding and release to the wild is a globally important conservation tool. However, captivity can result in phenotypic changes that incur post-release fitness costs, especially if they affect strenuous or risky behaviours. Bird wing shape is critical for migration success and suboptimal phenotypes are strongly selected against. In this study, I demonstrate surprising plasticity of bird wing phenotypes in captivity for 4/16 studied species. In a model species, captive-born juveniles with wild wing phenotypes (a 1-mm longer distal primary flight feather) survived post-release at 2.7 times the rate of those with captive phenotypes (i.e. a shorter distal feather). Subtle phenotypic changes and their fitness impacts are more common than widely realised because they are easily overlooked. To improve captive breeding for conservation, practitioners must surveil phenotypic changes and find ways to mitigate them.