This research project is funded by the Australian Research Council (ARC) in partnership with the International Fund for Animal Welfare (IFAW) and The Oceania Project (TOP). The research is a collaboration between Emeritus Professor Peter Baverstock and Professor Peter Harrison (SCU), Professor Scott Baker (University of Oregon), Mick McIntyre and Dr David Lavigne (IFAW), Trish and Wally Franklin (The Oceania Project), Dr Mel Norgate (Monash University), and other collaborators from the SCU Whale Research Centre.

Project Background

Measuring the age structure of wild animal populations is essential for understanding and predicting the dynamics of their populations, their growth rates and potential for recovery from exploitation, and estimating key life history parameters that underpin their management. Age structure data are particularly important for managing populations of endangered or vulnerable species such as humpback whales (Megaptera novaeangliae) to reduce the likelihood of further reductions in their populations, and to understand patterns of future recovery.

Unfortunately, determining the age of individuals in natural animal populations is often difficult or impossible using conventional ecological techniques. Long-term studies of marked individuals are expensive and time-consuming and usually involve only a small fraction of the whole population, while other techniques often require destructive sampling, which is clearly not appropriate for age determination in endangered species. Therefore, development of non-lethal techniques for measuring ages is becoming increasingly important, particularly with respect to cetaceans.

At present, odontocete toothed-cetaceans can be aged using growth layers in teeth and other features, but filter-feeding baleen whales lack teeth, hence alternative methods have been used for determining age. Previous data on age structure of baleen whale populations have been mainly derived from counting the numbers of layers in the wax plugs secreted in their ear canals, which were extracted from whale carcasses during commercial whaling operations last century. This process has been continued in the recent JARPA and current JARPAII Japanese pseudo-scientific whaling programmes, and extraction of earplugs for ageing whales has been used as a reason to justify their continued lethal catches. However, these age data have not been validated using other methods and the estimates of some parameters such as age at first reproduction have been questioned based on studies of living whales. Furthermore, the age structure of an exploited population is likely to differ substantially from that of a recovering population or stable population as it nears its environmental carrying capacity, and continued lethal catches significantly disrupt the age structure of the populations being studied, thereby confounding interpretation of population data.

Humpback whales were initially estimated to have a maximum lifespan of about 48 years based on earplug analyses, but the general consensus now is that they have a likely maximum age of at least 80 years, possibly longer. These long-lived mammals provide an excellent species for studying age, but are due to hunted as part of the JARPA2 programme during the forthcoming summer period in the Antarctic region. Therefore, the focus of this project on the evaluation of a non-lethal ageing technique for humpback whales is both scientifically interesting, and timely.

Project Aims and Objectives

The aim of this project is to determine the approximate age of individuals and the age structure of humpback whale populations recovering from exploitation, using non-lethal molecular ageing techniques.

The specific objectives of this project (and current status of the research) are summarised below:

1. Use standard telomere restriction fragment (TRF) analyses to quantify telomere lengths in humpback whale skin and tissue samples (Status: initial TRF analyses completed and telomere data successfully obtained from humpback whale samples);
2. Determine the relationship between telomere length and age using skin and tissue samples of humpback whales of known age or known minimum age (Status: analyses of samples from humpback whales of known age or known minimum age have been completed using both Southern blots and quantitative PCR techniques, and more detailed analyses are underway);
3. Validate telomere ageing using repeated samples from humpback whales of known age and known minimum age (Status: ongoing analyses);
4. Refine current telomere ageing techniques for use with cetaceans (Status: ongoing analyses);
5. Continue sampling humpback whales in Hervey Bay, Queensland, to collect sloughed skin samples from mothers and calves and individuals of known age or known minimum age as determined from the long-term resighting database and catalogue from The Oceania Project (Status: completed 10 week surveys in 2005 2006 and 2007 and beyond);
6. Use telomere data from large population samples to compare the age structure of humpback whale populations at different stages of recovery from previous exploitation (Status: planned once telomere-age relationships fully established);
7. Rapidly disseminate information on telomere ageing techniques and age structure of humpback whale populations to key decision makers to enable improved management of human impacts on humpback whales and other cetaceans, and to the wider scientific community through publications in peer-reviewed journals (Status: ongoing collaboration with IFAW).

Background information on telomeres

Recent research on telomeres in a wide range of other organisms has shown that telomere DNA sequences provide a potentially powerful new technique for estimating the age of individuals and for determining the age structure of populations in many species. Telomeres are short, repeated sequences of DNA and protein complexes located at the ends of chromosomes in eukaryotic organisms. The general structure of telomeres is similar in most species studied so far and the main telomere region consists of repeated units of DNA sequence and a sub-telomeric region adjacent to the main chromosome region. The DNA component of vertebrate telomeres is a highly conserved sequence TTAGGG, and identical sequences are found in a wide range of other organisms including slime moulds and fungi, while telomere sequences from many other eukaryotic organisms are remarkably similar.

During mitotic cell divisions the chromosomes undergo replication and telomeres have an essential role in the completion of DNA duplication and stabilise and protect the ends of chromosomes. However, the DNA sequences at the ends of chromosomes are not perfectly replicated due to the nature of the enzymic procedures involved. A consequence of this replication problem is that telomeres become progressively shorter each time a cell divides. Once the telomeres become too short, the chromosome ends are left unprotected and the cells reach their replication limit, which leads to cell death. In contrast, certain cell types such as cancer cells increase their telomere lengths via increased production of telomerase (an enzyme which increases telomere length) and are therefore potentially immortal. The progressive shortening of telomeres in many cell lines means that telomeres can be used as a measure of cellular age, and this cellular age should correlate with the age of the organism.

A lot of recent telomere research has focussed on human tissues and associated problems with cancer cells, and in humans a strong correlation between average telomere length and age has been demonstrated. Similar analyses have been done on other mammal species and telomere length also correlates with the age of individuals in mice, domestic cats, donkeys and horses. In birds, telomeres shorten predictably in some species (zebra finch, common terns, tree swallows), whereas in Leach's storm petrels telomeres lengthen with age.

In this study of telomere length in humpback whales we have shown for the first time that telomere DNA be detected and measured in whale skin samples, and we are now focussing on more clearly establishing the relationship between telomere length and age of humpback whales

Updated: 10 January 2011