Frogs | Bruce Waldman

Dr Bruce Waldman - Research in Behavioural and Population Ecology

Bruce Waldman
email | about

Our research on New Zealand frogs centres on animal behaviour and ecology, emphasising the relationship between behaviour, survivorship, and reproduction of individuals in natural populations.  We use genetic markers extensively to study the development of behaviour, its expression, and its fitness consequences. 

Our research is conducted at Lincoln University and Seoul National University.

Behaviour and Population Biology of Native New Zealand Frogs

Archey's frog, Leiopelma archeyi, from the Coromandel Peninsula

Native New Zealand frogs (genus Leiopelma) are among the rarest frogs in the world.  They are the living representatives of the most ancient lineage of frogs, closely resembling frogs that lived 200 million years ago.

We are studying the social behaviour of these unique frogs, including their paternal care of young, and their methods of communication (vocal and chemical) and orientation.  We are also studying genetic variation within and among localities to assess population viability and to determine how many species exist.

Archey's frogs are critically endangered.  We frequently find diseased, dying frogs in their natural habitat.  In our captive facility, we have brought the sick frogs back to health and have successfully bred them (news story).  Breeding frogs with disease-resistant genes may offer some hope to save the species (news story).

Sadly, despite the advances that we made, the extinction of this 'living fossil' species may be imminent (news story).
More details on this research.

Why Are New Zealand Frog Populations Vanishing?

Green and Golden Bell frog, Litoria aurea, infected with chytrid fungus, from the Bay of Plenty.

Emerging infectious diseases increasingly are being linked with reports of mortality in amphibians.  In 1999, we first discovered chytrid fungus causing morbidity and mortality in populations of wild Litoria frogs.  We are tracking the spread of these pathogens in New Zealand, and we are evaluating the risk they pose to native frogs.

Our most recent findings suggest that native frogs in the wild rarely are infected by chytrid fungus and show no clinical signs of chytridiomycosis.  Nonetheless, Archey's frogs are infected by a variety of bacteria, viruses, and other fungi, suggesting that their immune systems are compromised in the wild.  We are planning research to identify toxins that may be responsible for the observed population declines. More details on this research.

Other possible factors, including effects of pesticides and herbicides, pollutants and endocrine disruptors, habitat destruction, and exotic predators, are also being studied by members of our research group.

Conservation Genetics and Behavioural Ecology

American toad, Bufo americanus, from Concord, Massachusetts, USA

Using modern molecular techniques, we study basic characteristics of population structure to determine risks posed to threatened species by genetic homogeneity and inbreeding.

We measure dispersal patterns, the extent to which animals inbreed, their effective population sizes, and levels of genetic differentiation within and among populations.  We are testing whether progeny of closely related parents suffer from inbreeding depression.

Projects currently underway include studies of New Zealand grand skinks (Oligosoma grande) and North American and Asian toads (Bufo boreas, B. americanus, B. gargarizans, and B. stejnegeri). More details on this research.

Kin Recognition and the Evolution of Disease Resistance

Western toad, Bufo boreas, outside Livermore, California, USA Photograph by Joyce Gross (University of California, Berkeley) who assisted us in fieldwork

Many animals recognise their close relatives. Kin discrimination facilitates cooperation among close relatives, and the avoidance of close relatives as potential mates.

We are studying the genetic basis of kin recognition in frogs by analysing the behaviour of individuals with known histocompatibility types. We are studying influences of genetic similarity on interference competition, social cooperation, mate choice, and disease resistance.

In a project supported by the Marsden Fund, we are examining how social behaviour and immune system function co-evolve to ensure the health of individuals and the viability of populations.

In a project supported by the National Research Foundation of Korea, we are studying how immune system genes rapidly evolve in frog populations exposed to emerging infectious pathogens.

South African clawed frog, Xenopus laevis, tadpole isogenic for MHC haplotype

Lincoln University hosts an internationally important colony of Xenopus laevis frogs that were transferred to us from the Basel Institute for Immunology when it closed.  The colony includes unique immunological strains of frogs held nowhere else in the world.  It thus serves as a key biological resource for frog researchers worldwide.

Take a virtual tour of our laboratory and its members

Returning from a field trip

Our research group is working on a variety of projects aside from those described above.  Click here to meet our staff and students, and to read details of what they are doing.

On the right are laboratory members Lino Ometto, Henriette Beikirch, and Jandouwe Villinger, just returning from a field trip searching for the elusive South Island Leiopelma frog (photograph taken by Dan Buchholz, NIH, Bethesda, Maryland, USA, who accompanied us).