- Title
- Investigating and integrating animal behaviour in the conservation and management of an endangered amphibian
- Creator
- James, Melanie Sandra
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2019
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- The Earth is experiencing a period of mass extinction due to human development and expansion (Wake & Vredenburg 2008). It has been estimated that 866 animal, plant, fungi and protist species have become extinct in recent history, and 25,821 species were declared either Critically Endangered, Endangered or Vulnerable in 2017 (IUCN 2017). Causal agents of population declines and biodiversity loss include climate change, land clearing, habitat modification and the introduction of exotic competitor or predator species (Vitousek et al. 1997) and disease (Skerratt et al. 2007) which affect species from global to local scales. The magnitude of species loss and threat of further extinctions has caused worldwide attention, instigating efforts to identify and conserve species at risk (Redford & Richter 1999). Species management programs typically aim to identify causal agents of decline, assess species requirements for survival and reproduction and understand population proce sses so that informed decisions can be made to reverse population declines. An important step in this process is gaining an understanding of the factors which affect species distribution (Guisan et al. 2013; Noss et al. 1997). Conservation programs often aim to understand an animal’s distribution by identifying what constitutes habitat. Factors commonly examined include abiotic and biotic attributes of the landscape including available shelter and food, as well as an animal’s interaction with heterospecifics (Campomizzi et al. 2008). In the instance that these factors or interactions correlate with species presence or abundance either positively or negatively, it is assumed that these factors are actively selected for or avoided (Batt 1992). However, additional behavioural factors can affect distribution, such as attraction to (Ahlering et al. 2010) or avoidance of conspecifics (same species) (Keren-Rotem et al. 2006; Stamps 1983), causing strong aggregations or segregation of animal distribution over a landscape, respectively. Despite the influence of these factors on distribution, conspecific attraction and avoidance are not commonly considered by conservation programs when attempting to understand, predict and alter species distributions (Campomizzi et al. 2008). As animals experiencing conspecific attraction or avoidance may deviate from the correlation model assumed by habitat selection, research programs aimed at assisting endangered species cannot afford to ignore conspecific interactions (Manly et al. 2009). A last resort for conservation initiatives is breeding animals in captivity, creating or restoring habitat and translocating animals back into populations that are experiencing population decline or have become locally extinct. Current research in conservation biology has focused on identifying and assessing animal behaviour which can limit the success of conservation initiatives such as; multi-spatial-level habitat selection (McGarigal et al. 2016), conspecific attraction (Campomizzi et al. 2008) and mate selection within captive breeding (Chargé et al. 2014a; Chargé et al. 2014b). As these factors influence species distribution and survival, they therefore affect the success of habitat construction programmes and the persistence of naturally occurring or translocated populations. Amphibians are a globally threatened taxon with 33 extinct species and 2,100 species declared either critically endangered, endangered or vulnerable (IUCN 2017). Factors causing amphibian decline include the human facilitated spread of chytrid fungus (Batrachochytrium dendrobatidis) (Skerratt et al. 2007), global climate change, introduced species as well as habitat loss and modification (Brown et al. 2012; Stuart et al. 2004). Considerable research has been undertaken on causal agents of decline, along with understanding population processes and habitat requirements that affect the persistence of populations (Wake & Vredenburg 2008). Despite the fact that many amphibian species show signs of conspecific attraction and/or avoidance, the influence of conspecific interactions on spatial distribution and subsequent declines of amphibians is under-investigated. This current research project explores the potential for particular behaviours which may influence species distribution and the success of habitat creation and translocation programmes for the green and golden bell frog (Litoria aurea). For the first research paper, I assessed conspecific call attraction in L. aurea. Over a landscape, animal distributions can be skewed as a result of conspecific attraction and aggregation. This can hinder habitat restoration and creation programmes as species may fail to colonise available habitat, despite its suitability. It has been noted from past research that L. aurea uses particular habitat and has distributional traits which suggest the presence of conspecific attraction, and using speakers playing calls can successfully attracted L. aurea at short distances, forming new aggregations (James et al. 2015: Attachment 1). In the first research chapter, I aimed to use speaker systems playing calls to manipulate the landscape distribution of L. aurea. I placed a stand with a speaker playing call broadcast in a treatment waterbody (T), a stand with no calls broadcasted as a manipulative control (MC) and no stand or speakers as a control (C). This design was replicated in five areas on Kooragang Island, Australia, and waterbodies were surveyed to measure changes in abundance and calling over two and a half breeding seasons. We found that speaker introduction did not increase abundance or calling at T relative to MC and C. We did, however, find that the length of time males called was longer at T, compared to MC and C. As the length of calling time may be extended using conspecific call broadcast , provision of conspecific stimulation at translocation sites may improve breeding activity and retention of the population post-release by reducing dispersal. For the second research chapter, I assessed habitat selection of L. aurea. The site selection of breeding individuals is a crucial component of a species habitat selection and can help to direct conservation programmes. However, very little is known about the microhabitat selection of calling male L. aurea. This study aimed to distinguish if male aggregations are associated with specific habitat features within a waterbody and describe their use of available habitat structures. Within waterbodies we compared calling locations relative to non-calling locations for water variables (temperature, salinity, dissolved oxygen), microclimate (temperature, humidity, average and maximum wind speed) and habitat (percentage coverage of water, ground, emergent vegetation and floating vegetation). Overall, males were associated with lower salinity and higher dissolved oxygen, higher percentage coverage of emergent vegetation and bare ground, and low percentage coverage of open water. Males were most commonly found in the water floating between or beside emergent vegetation or perched on emergent vegetation above water level. This suggests that males may select habitat to protect themselves from predators, or for breeding; providing appropriate vegetation, dissolved oxygen and salinity for embryo and tadpole development. This provides supportive information for previous studies on habitat selection, indicating what habitat is preferred by breeding males to improve monitoring, habitat creation and rehabilitation. For the third research chapter, I assess a habitat construction programme. Habitat creation programmes are often used to compensate for the loss of habitat for endangered species, with varying results. I describe an early stage wetland construction programme implemented for L. aurea on Ash Island, NSW Australia. Seven ephemeral (flooding) and two permanent waterbodies were constructed near an existing population. The wetland was designed to increase landscape aquatic habitat, based on adaptive management learnings from past research. In this study, I assess the initial use of this habitat by L. aurea, and initial findings on the design suitability. Surveys in constructed wetlands and in the broader Kooragang area showed that L. aurea rapidly colonised and called at constructed ephemeral wetlands but not permanent wetlands. The chorus size in constructed wetlands was large in comparison to other populations in coastal NSW, and a range of other frog species also bred onsite. Female L. aurea used a nearby remnant wetland (adjacent to the constructed wetlands), and used different habitat to males. Similar habitat use variation between sexes was reflected in the broader population. Most male and female L. aurea captured on Ash Island were under 12 months of age, and body condition in the constructed wetlands was higher than in the broader population. Waterbody design successfully protected waterbodies from overland flooding, and ephemeral waterbodies dried, which suggests the drying regime may protect the constructed habitat long-term from infestation of predatory fish. Elevated salinity from ground water in permanent waterbodies (intended to ameliorate chytrid disease in the landscape) was higher than anticipated and requires further monitoring. It is hoped that this programme may help guide other conservation projects creating habitat for amphibians under threat. For the fourth research paper, I assess sexual selection in L. aurea. As a conservation strategy for L. aurea, captive breeding programmes supplement at-risk populations and translocate individuals to their former ranges. However, breeding programmes are undertaken with very little information on sexual selection and its exclusion can reduce the fitness of released animals. The aim of the fourth study was to assess whether forms of sexual selection occur for L. aurea to inform captive breeding programmes. In the wild I studied mate selection. Firstly, we aimed to assess if the size and body condition of amplexing individuals (grasping to breed), differed from other individuals in the population as an indication of female sexual selection or male-male competition. Secondly, we investigated if male and female amplexing pairs were size correlated as an indicator of size assortative mating, and thirdly we made observations on behavioural interactions in the breeding waterbody to complement the analysis. In Whangarei, New Zealand, we captured L. aurea over 4 survey nights, undertaking capture-mark-recapture and measuring morphometrics of snout vent length (SVL), right tibia length (RTL) and weight, calculated body condition. We compared the SVL, RTL and weight of breeding individuals to non-breeding individuals and found that amplexing males were larger with better body condition, however, female size did not differ. Male-female pairs were not size assortative and aggressive interactions were recorded between males. Larger male size may be an indicator of either female selectivity or larger-male mating advantage through aggressive interactions. As removal of sexual selection in captive breeding programmes can reduce fitness and place conservation initiatives at risk, I recommend incorporating sexual selection by placing multiple males of varying sizes in breeding tanks with females to facilitate female selectivity or larger-male mating advantage. Based on the results of the current studies, I have identified possible constraints on the use of conspecific attraction for this species, and also recognised its potential use in translocations programmes to improve project outcomes. As a result of microhabitat assessment, habitat creation and management programmes can use specific parameters to design, maintain and monitor habitat for calling males. Assessment of a habitat construction project designed from previous research recommendations shows initial project success and provides information to refine future habitat construction programmes. Finally, assessment of sexual selection in L. aurea provides vital information to conservation programmes breeding animals for translocation to work toward improving the fitness of released individuals. Overall, the current study provides key aspects of L. aurea’s biology and ecology that have not been clearly addressed in the literature and aims to improve conservation efforts. In light of recent extinctions and increasing pressures on wildlife, continued research on key threatening processes and behavioural ecology is crucial to help guide conservation.
- Subject
- wetlands; habitat selection; population; distribution; extinction; endangered species; habitat creation; green and golden bell frog; Litoria aurea; amphibian; frog; environment; reintroduction; Sydney Olympic Park; Kooragang Island; New Zealand; Australia; New South Wales; captive; translocation; conservation; sexual selection; breeding; behaviour; conspecific attraction; aggregation
- Identifier
- http://hdl.handle.net/1959.13/1401338
- Identifier
- uon:34893
- Rights
- Copyright 2019 Melanie Sandra James
- Language
- eng
- Full Text
- Hits: 4000
- Visitors: 3898
- Downloads: 280
| Thumbnail | File | Description | Size | Format | |||
|---|---|---|---|---|---|---|---|
| View Details Download | ATTACHMENT01 | Thesis | 2 MB | Adobe Acrobat PDF | View Details Download | ||
| View Details Download | ATTACHMENT02 | Abstract | 453 KB | Adobe Acrobat PDF | View Details Download |