Behavioural Ecology and Biomechanics

Dr Aaron Harmer

Research Officer

School of Natural and Computational Sciences

Massey University

Auckland, New Zealand

I am an entomologist at Massey University in Auckland, New Zealand. My research integrates behavioural and biomechanical approaches to address key questions in the evolution of form-function relationships across taxa.

Some of my previous research has explored the role of silk properties and web architecture in the ecology and evolution of orb-web spiders. My current focus is on how the mechanical performance of animal weapons coevolves with their function.

I also have a strong background in behavioural ecology and dabble in a range of topics including video tracking animals in R, bird song and behaviour, and animal personality (with a bit of photography on the side).

Group members

Mac McKay - Masters

My Masters project is investigating the factors influencing success and failure of recruitment in the Tuturuatu (shore plover) on Motutapu island. The first phase of the project is currently underway and involves recording the behaviour of tuturuatu and their interactions with other species both by direct observation and with hidden cameras. The second phase will be to follow a cohort of captive-bred juvenile birds after their release on the island in late January.

Yasmin Singh - Masters

My Masters research is investigating wētā behaviour and habitat-use in response to predator exposure. I am focusing on two North Island species from different groups: the Auckland tree wētā (Hemideina thoracica) and a giant wētā, the wētāpunga (Deinacrida heteracantha). The main part of my research is focused on responses to mammalian predators in Auckland tree wētā by comparing behaviour and habitat use across pest-free and pest-infested sites.

Co-supervised PhD students

Michelle Roper - Completed 2019

Sexual dimorphism of song and life history trade-offs in the New Zealand bellbird

Wesley Webb - Completed 2020

Cultural evolution of song diversity in New Zealand bellbird (Anthornis melanura)

Mehrnaz Tavasoli

Behavioural plasticity in common blackbird (Turdus merula): exploration, responses to novelty, and reproductive success

Abigail Kuranchie

Assessing the role of marginal and degraded habitats in species conservation

Jacques De Satge

The function of New Zealand mangrove forests as wildlife habitats and effect of mangrove removal on banded rails (Gallirallus phillippensis)

Irene Middleton

Detecting and predicting the dispersal and naturalisation of foreign marine species on New Zealand reefs


Behaviour and fight mechanics of Auckland tree wētā

Despite being reasonably common, Auckland tree wētā are surprisingly under-studied, with little published research on their natural history and behaviour. We are exploring several aspects of Auckland tree wētā behavioral ecology including the distribution of adult male size dimorphism, antagonistic interactions between males, and habitat space use. We are also modelling the mechanics of the large weaponised jaws of males during contests.

Biomechanics of traumatic insemination in Coridromius plant bugs

Traumatic insemination (TI) is relatively rare form of mating among animals, but has arisen multiple times within Cimicomorpha bugs, most famously in Cimex bed bugs. While most TI taxa show low diversity in male genitalia (usually a simple hypodermic sickle-like structure), Coridromius plant bugs are hugely diverse in both male genitalia and female paragenitalia. Some species show little specialisation in shape, while others appear to behave more like classical lock and key mechanisms. In collaboration with Dr Nikolai Tatarnic (Western Australian Museum), we are investigating the relationship between the mechanical performance of male genitalia as piercing structures, and the degree of specialisation in female counter-adaptations.

Biomechanics of sexually selected weapons in New Zealand harvestman

While some secondary sexual traits are adapted for mating or courtship, others are used in intra-sexual conflict. In collaboration with A/Prof. Greg Holwell (University of Auckland) and Dr Christina Painting (University of Waikato), we are investigating the mechanical performance of the absurdly exaggerated chelicerae of duelling harvestman Pantopsalis, Fosteropsalis). Males exhibit weapon trimorphism, with two exaggerated morphs and a third reduced morph. Males with different exaggerated morphs employ different behavioural strategies during fights. We are interested in how behavioural strategies used during sexual conflict correlate with mechanical performance, and have likely shaped the evolution of their extreme weaponry.

Visualising and analysing animal movement patterns is essential to many behavioural studies. While commercial options exist for analysing animal movement via video, the cost of these is often prohibitive. To meet the need for an efficient and cost-effective video tracking and analysis tool, we have developed the 'pathtrackr' package for the open-source programming environment R. The 'pathtrackr' package allows for an automated and consolidated workflow, from video input to statistical output, of an animal's movement. The tracking functions work across a variety of visual contexts, including heterogenous backgrounds and variable lighting, and can deal with small amounts of localised background movement. The 'pathtrackr' package is available on github.

Spider web evolution

Spider orb-webs are the ultimate anti-ballistic devices, capable of dissipating the relatively massive kinetic energy of flying prey. We integrated biophysical and ecological data and models to test a major prediction of the rare, large prey hypothesis, that selection should favour webs with increased stopping capacity and that large prey should comprise a significant proportion of prey stopped by a web. We found that larger webs indeed have a greater capacity to stop large prey. However, based on prey ecology, we also found that these large prey make up a tiny fraction of the total biomass potentially captured. We concluded that large webs are adapted to stop more total biomass, and that the capacity to stop rare, but very large, prey is an incidental consequence of the longer radial silks that scale with web size.


Please contact me if you are interested in working in our group

Beetle feeding mechanics

Evolutionary relationship between beetle feeding ecology and mandibular form and function. New Zealand beetles are incredibly diverse with many ancient lineages that are unknown elsewhere. This research will employ 3D geometric morphometrics to understand how feeding specialisation correlates with morphospace occupation in staphylinid beetles.