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Infrared Forum Research and Applications infraR&D

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Thermal Imaging and Wildlife Biology

Dominic J. McCafferty1 & John I. Currie2

1School of Education, University of Glasgow,

Glasgow G3 6NH , Scotland, UK

2Scottish Energy Centre, Edinburgh Napier University, Merchiston Campus,

Edinburgh, Scotland, UK

Introduction

Thermal imaging has been successfully used since the 1950s to undertake research on captive and wild animals. Applications have involved population monitoring, to study metabolic heat loss and to investigate disease and injury in a range of species. The main advantage of this technique for research on animals is that it provides accurate non invasive measurements with high spatial resolution. This allows for detection of animals at a distance and to identify thermal patterns associated with blood circulation. Thermal imaging has been relatively restricted in the past due to cost and portability of devices. However, development of new technology has increased its use in laboratory and field research. There is now considerable scope for further research using this technology.

Thermal Physiology

Fig 1. (A) Thermal image of rabbit (Oryctolagus cuniculus) revealing underlying blood circulation to ears for dissipation of excess body heat. (B) Zebras (Equus burchelli boehmi) in full sun demonstrating how differential absorption of solar radiation by black and white coat produces warm and cool surface temperature patterns. Thermal imager: FLIR PM595.

Thermal imaging provides the opportunity of measuring the surface temperature of an animal and thereby indirectly reveals the pattern of underlying blood flow, depending on the distribution of insulation provided by fur or feathers (Fig. 1A). It has therefore been used to examine many different aspects of thermal biology, investigating anatomical, physiological and behavioural adaptations of cold (ectothermic) and warm (endothermic) blooded animals (Fig. 2). Researchers must take into account the physiological and behavioural state of the animal and the effects of coat colour on radiative warming (Fig. 1B). Nevertheless, this may be overcome by standardising measurement conditions and recording at night or in the shade.


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Fig. 2. Sequence of images of a barn owl (Tyto alba) in flight. This demonstrates how thermography can be used to examine exercise physiology of free ranging species. Thermal imager: AGA 782 Thermovision.

Animal Health and Welfare

There has been considerable use of thermal imaging as a diagnostic tool in veterinary examinations. This

has been especially useful in equine medicine where disease and injury can be detected by the non

symmetrical surface temperature pattern on limbs. More recently this has been extended to examine the

health of wild animal populations. For example, it can be used to monitor inflammation, infection and

tissue repair processes (Fig. 3).

Fig. 3. The use of thermography to examine the response of grey seal (Halichoerus grypus) pups to flipper tagging. Surface temperature is used as a proxy for monitoring inflammation and infection. Circles highlight the areas for comparison between adjacent sections of the flipper. This diagnostic method indicated that healing occurs relatively rapidly in this species. Thermal imager: FLIR E300.

Counting Animal Populations

Population counts of wild birds and mammals have been made by thermal imaging surveys. This is suitable

for species that are difficult to observe due to cryptic colouration or species that are nocturnal (Fig. 4).

High thermal contrast is required against a cool substrate or cold sky. Thermal surveys are not appropriate

with continuous vegetation cover or where strong solar radiation reduces thermal contrast. Thermal

imaging is generally undertaken by aerial surveys and systems are used manually to locate and count

colonies. One of the most extensive applications of this technique is for the census of seals in the UK


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(www.smru.st-andrews.ac.uk). In some cases specialised automatic image detection systems are employed

for fast moving animals such as bats.

Fig. 4. Visual and thermal images of harbour seals (Phoca vitulina) showing that thermal cameras are able to detect well camouflaged animals against a cool background. Thermal imager: FLIR P65, 120mm lens.

Research Needs

The development of new thermal imaging technology has allowed thermography to be more widely adopted by researchers in the field of wildlife biology. Most applications work with still image capture but studies could be enhanced by real time recording of thermal images so that greater temporal patterns can be determined. The ability to record both thermal and visual images simultaneously on the same device would allow more accurate recording and integration of behaviour and temperature measurement.

Counting wild animal populations using thermal imaging is currently a highly successful method of monitoring several large animal populations. However, there is considerable scope for the further use of this technique. The first of these will be for remotely operated devices from fixed locations that can transmit data by mobile phone networks or satellite communication. These systems must be robust and withstand hostile environments and will be suitable for example, for avian surveys (Fig. 5). The second application will be for aerial surveys that deploy surveillance type technology, mounted externally on aircraft. Although these systems are in place by national agencies for surveillance, at present this technology is not widely available to field researchers. Both the above applications will require appropriate image analysis software with automated identification of target species. This will allow fast processing of datasets and increase the efficiency of thermal surveys.

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Fig. 5. Flock of pigeons (Columba livia) showing good thermal contrast appropriate for population counts. Thermal imager: FLIR E300.

Conclusions

Thermal imaging is becoming an increasingly popular choice for wildlife biologists undertaking research on free ranging species. The ability to record surface temperature without the need to capture and handle animals is important for measurement accuracy and animal welfare. It is hoped that new thermal surveillance technology will become available to improve the efficiency of surveying wild animal populations.

Further Reading

McCafferty, D.J. 2007. The value of infrared thermography for research on mammals: previous applications and future directions. Mammal Review 37: 207-223.

http://dx.doi.org/10.1111/j.1365-2907.2007.00111.x

Paterson, W., Pomeroy, P.P., Sparling, C.E., Moss, S., Thompson, D. Currie, J.I. & McCafferty, D.J. In Press. Assessment of flipper tag site healing in gray seal pups using thermography. Marine Mammal Science. http://dx.doi.org/10.1111/j.1748-7692.2010.00400.x

Authors

Dominic McCafferty

Dominic J. McCafferty is lecturer in animal ecology on the Certificate of Higher Education Programme in the School of Education and Honorary Senior Research Fellow in the School of Life Sciences.

Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow G12 8QQ, Scotland, UK School of Education, University of Glasgow, 11 Eldon Street, Glasgow G3 6NH, Scotland, UK Email: [email protected] http://www.gla.ac.uk/schools/education/staff/dominicmccafferty/

John Currie

Scottish Energy Centre, Edinburgh Napier University, Merchiston Campus, Colinton Road, Edinburgh, Scotland, UK. Email: [email protected]

http://www.napier.ac.uk/randkt/rktcentres/sec/Our%20Team/Pages/JohnCurrie.aspx

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