Tracey Leeanne Rogers

UNSW Sydney | UNSW · Evolution & Ecology Research Centre

It is proposed that where sexually selected vocal communication is an honest signal, the call production rate is predicted to change throughout the breeding season. Male leopard seals call underwater for many hours each day over their three- to four-month breeding season, and it is hypothesised that a decrease in calling rate would be associated wi...

Understanding species distribution and behavior is essential for conservation programs of migratory species with recovering populations. The critically endangered Antarctic blue whale (Balaenoptera musculus intermedia) was heavily exploited during the whaling era. Because of their low numbers, highly migratory behavior, and occurrence in remote are...

Biological markers (biomarkers) are invaluable and widely adopted in ecology, archaeology, and anthropology. Serially sampling biomarkers along continuously growing inert tissue, such as vibrissae, hair, nail, horn, or baleen, is an ideal method by which to capture the changes in an individual's diet, environment, climate, health, and stress levels...

Previous studies of the vocalisation frequencies of mammals have suggested that it is either body mass or environment that drives these frequencies. Using 193 species across the globe from the terrestrial and aquatic environments and a model selection approach, we identified that the best supported model for minimum and maximum frequencies for voca...

Context. The value of captive breeding for recovery programs of endangered carnivorous mammals is often questioned because of low post-release survival reported for founder animals following translocation. Aims. The aim of the present study was to test the effect of rearing method on survival and body mass of captive-raised Tasmanian devils (Sarcop...

Animals that rely extensively on scavenging rather than hunting must exploit resources that are inherently patchy, dangerous, or subject to competition. Though it may be expected that scavengers should therefore form opportunistic feeding habits in order to survive, a broad species diet may mask specialization occurring at an individual level. To t...

The quantitative use of stable isotopes (SIs) for trophic studies has seen a rapid growth whereas fatty acid (FA) studies remain mostly qualitative. We apply the Bayesian tool MixSIAR to both SI and FA data to estimate the diet of three sympatric predators: the crabeater (Lobodon carcinophaga), Weddell (Leptonychotes weddellii) and leopard seal (Hy...

Individual longitudinal records of diet, movement, and physiological state of endangered Tasmanian devils (Sarcophilus harrisii) are needed for effective management of wild populations, yet most traditional techniques are expensive or labor‐intensive. Stable isotope analysis of inert tissue, such as vibrissae (whiskers), provides a viable and minim...

This informational article provides an overview of the geographical range, habitat, ecology, management and conservation challenges of leopard seals. It is a peer-reviewed online article posted on the SCAR Antarctic Environments Portal here: https://environments.aq/publications/leopard-seal-hydrurga-leptonyx/

Pinnipeds (true seals, sea lions and walruses) inhabit two thermally different environments, air and water, so need to make continuous adjustments to maintain a balanced body temperature. The thermal isolation properties of thick blubber keep warmth within the body’s core, ideal for mammals while in the water; however, when on land, this thick blub...

We test the performance of the Bayesian mixing model, MixSIAR, to quantitatively predict diets of consumers based on their fatty acids (FAs). The known diets of six species, undergoing controlled-feeding experiments, were compared with dietary predictions modelled from their FAs. Test subjects included fish, birds and mammals, and represent consume...

Fatty acids have been widely used as trophic biomarkers in marine mammals. However, for the South American sea lion, the most abundant otariid in the eastern South Pacific, there is no information about blubber fatty acids and their link to diet. Here, we compare fatty acid profiles of sea lions from two distinct oceanographic regions in northern a...

The number of social contacts of mammals is positively correlated with the diversity of their gut microbes. There is some evidence that sociality also affects microbes in the respiratory tract. We tested whether the airway microbiota of cetacean species differ depending on the whales’ level of sociality. We sampled the blow of blue (Balaenoptera mu...

Background: Most fatty acids (FAs) making up the adipose tissue in mammals have a dietary origin and suffer little modification when they are stored. However, we propose that some of those FAs, specifically those that can be synthesised or modified by mammals, are also being influenced by thermal forces and used as part of the mechanism to regulate...

Global warming, and its consequences, constitute one of the main stressors for organisms worldwide, affecting different factors such as the geographic distribution and the abundance of parasites, which in turn can affect the immune system of their hosts, and vice versa. Therefore, it is important to have baseline information on immune parameters of...

Cetacean represent vulnerable species impacted by multiple stressors, including reduction in prey species, habitat destruction, whaling and infectious disease. The composition of blow microbiota has been claimed to provide a promising tool for non-invasive health monitoring aiming to inform conservation management. Still, little is known about the...

The foraging behaviors of apex predators can fundamentally alter ecosystems through cascading predator–prey interactions. Food caching is a widely studied, taxonomically diverse behavior that can modify competitive relationships and affect population viability. We address predictions that food caching would not be observed in the marine environment...

Restrictions on roaming Until the past century or so, the movement of wild animals was relatively unrestricted, and their travels contributed substantially to ecological processes. As humans have increasingly altered natural habitats, natural animal movements have been restricted. Tucker et al. examined GPS locations for more than 50 species. In ge...

In the present study we used stable carbon (δ¹³C) and nitrogen (δ¹⁵N) analysis of whiskers to investigate the isotopic niche overlap and partition among three pack ice seals sampled along the Danco Coast, Western Antarctic Peninsula (WAP). Isotopic values in serially sampled whiskers of 34 leopard (Hydrurga leptonyx, HL), 13 crabeater (Lobodon carc...

The study of marine soundscapes is a growing field of research. Recording hardware is becoming more accessible; there are a number of off-the-shelf autonomous recorders that can be deployed for months at a time; software analysis tools exist as shareware; raw or preprocessed recordings are freely and publicly available. However, what is missing are...

The study of blubber fatty acids (FAs) has attracted increasing scientific interest due mainly to its potential use as trophic markers. This is possible because most FAs are transferred unmodified from the prey to the blubber of the predator. Additionally, FAs have also been used to understand other aspects of the biology of marine mammals, includi...

Occupying about 14 % of the world's surface, the Southern Ocean plays a fundamental role in ocean and atmosphere circulation, carbon cycling and Antarctic ice-sheet dynamics. Unfortunately, high interannual variability and a dearth of instrumental observations before the 1950s limits our understanding of how marine–atmosphere–ice domains interact o...

Supporting Information S2. A comparison of the level of support for possible explanatory models that describe the evolution of the a) minimum and b) maximum frequency in vocalisations of mammals.

Supporting Information S1. List of references for frequency data.

Occupying 14% of the world’s surface, the Southern Ocean plays a fundamental role in global climate, ocean circulation, carbon cycling and Antarctic ice-sheet stability. Unfortunately, high interannual variability and a dearth of instrumental observations before the 1950s limits our understanding of how marine-atmosphere-ice domains interact on mul...

Leopard seals (Hydrurga leptonyx) produce sequences of stereotyped sounds, or bouts, during their breeding season. The seals share common sounds but combine them in individually distinctive sequences. This study examines the underlying structure of the calling bouts by estimating the information entropy of the sound sequences with three entropy est...

Predator-prey relationships play a key role in the evolution and ecology of carnivores. An understanding of predator-prey relationships and how this differs across species and environments provides information on how carnivorous strategies have evolved and how they may change in response to environmental change. We aim to determine how mammals over...

Transfrontier wildlife corridors can be successful conservation tools, connecting protected areas and reducing the impact of habitat fragmentation on mobile species. Urban wildlife corridors have been proposed as a potential mitigation tool to facilitate the passage of elephants through towns without causing conflict with urban communities. However...

The analysis of blubber fatty acids (FAs) is a useful tool to infer diet of mammals that live in remote regions where year-round studies are difficult. The FA may not be distributed uniformly within the blubber, which can have implications for dietary predictive studies. The aim of this study was to determine the FA composition in the blubber core...

A single male Australian sea lion (Neophoca cinerea) was tested for its auditory sensitivity to in air sound. Short, broadband clicks were presented via headphones while the animal was immobilized during medical treatment. Click-evoked auditory brainstem responses (ABRs) were recorded in the animal after acoustic stimulation at decreasing sound pre...

For effective species management, understanding population structure and distribution is critical. However, quantifying population structure is not always straightforward. Within the Southern Hemisphere, the blue whale (Balaenoptera musculus) complex is extremely diverse but difficult to study. Using automated detector methods, we identified " acou...

We examined recordings from a 15-month (May 2009–July 2010) continuous acoustic data set collected from a bottom-mounted passive acoustic recorder at a sample frequency of 6 kHz off Portland, Victoria, Australia (38°33′01″S, 141°15′13″E) off southern Australia. Analysis revealed that calls from both subspecies were recorded at this site, and genera...

Marine mammals are globally significant because of their sensitivity to environmental change and threatened status, often serving as ‘ecosystem sentinels’. Disease is a major cause of marine mammal population decline and the role of the microbiome in disease has generated considerable interest. Recent research in humans has greatly enhanced our und...

Rapid changes to climate in the western Antarctic Peninsula region over the last 50 yr, which have led to decreases in the extent and duration of sea ice, are likely to have significant impacts upon the Antarctic ecosystem as a whole. Understanding the behaviour of higher trophic level animals occupying these regions is important, as they may be in...

Predator-prey relationships and trophic levels are indicators of community structure, and are important for monitoring ecosystem changes. Mammals colonized the marine environment on seven separate occasions, which resulted in differences in species' physiology, morphology and behaviour. It is likely that these changes have had a major effect upon p...

Leopard seals (Hydrurga leptonyx) are top predators in the Antarctic ecosystem. They produce stereotyped calls as part of a stylized underwater vocal display. Understanding of their acoustic behavior is improved by identifying the amplitude of their calls. The amplitude of five types of calls (n = 50) from a single male seal were measured as broadb...

The leopard seal, Hydrurga leptonyx, is an apex predator that has a key role as consumer within the Antarctic ecosystem. Due to the constraints of traditional methods for studying feeding ecology fatty acids (FAs) analysis of blubber has become a useful tool for determining diet since it provides an indication of long-term dietary histories. FAs ho...

Predator-prey body mass relationships are a vital part of food webs across ecosystems and provide key information for predicting the susceptibility of carnivore populations to extinction. Despite this, there has been limited research on the minimum and maximum prey size of mammalian carnivores. Without information on large-scale patterns of prey ma...

Deployments of ARGOS satellite transmitters on 19 post-breeding adult southern elephant seal males at King George Island / Isla 25 de Mayo in November 2013 represent a follow-up study of earlier projects on post-moulting adult males satellite tagged in 2000 and 2010. These previous deployments were constrained by the fact that only a small fraction...

Background / Purpose: The factors driving the evolution of acoustic behaviour in mammals remain unresolved. Conflicting hypothesis, the size-frequency allometry hypothesis and acoustic adaptation hypothesis, predict that body size or alternatively the environment have driven the design of acoustic signals. The movement of mammals from land to sea...

AimMammalian home range patterns provide information on spatial behaviour and ecological patterns, such as resource use, that is often used by conservation managers in a variety of contexts. However, there has been little research on home range patterns outside of the terrestrial environment, potentially limiting the relevance of current home range...

Thylacinidae is an extinct family of Australian and New Guinean marsupial carnivores, comprizing 12 known species, the oldest of which are late Oligocene (∼24 Ma) in age. Except for the recently extinct thylacine (Thylacinus cynocephalus), most are known from fragmentary craniodental material only, limiting the scope of biomechanical and ecological...

Context Three dolphin species occur in coastal waters of monsoonal northern Australia: the Australian snubfin (Orcaella heinsohni), humpback (Sousa sp.) and the bottlenose (Tursiops sp.). Their overall population size and trends are poorly known, and their conservation status has been difficult to resolve, but can be expected to deteriorate with li...

On a global scale, the coastal waters of the Northern Territory (NT), Australia, are relatively undisturbed, but the pace and extent of coastal development is increasing. Three species of dolphin occur in these waters: the Australian snubfin Orcaella heinsohni, Indo-Pacific humpback Sousa chinensis and bottlenose Tursiops sp., but their distributio...

Leopard seals (Hydrurga leptonyx) produce underwater vocalizations during the breeding season in austral summer. Due to their solitary oc currence and remote habitat, hydroacoustic observations are an important technique to investigate this species regarding their population structure and acoustic ecology. This study examines, whether the acoustic...