Monitoring of Wildlife Populations
Wild animal populations may be monitored for a variety of reasons: biological interest or research purposes (eg bird migration); game management (eg deer); the wild animal may be considered an actual or potential pest (eg rodents, birds); the species may be endangered or threatened and the population is being monitored to assess its progress or recovery; the biological diversity or ‘ecological health’ status of an area may be required; or perhaps it is desirous to know the effects of human management actions, land-use practices, or alternative activities on one or more species (Witmer, 2005).
To monitor a wild animal population information about the animal(s) of interest first needs to be collected. This is commonly achieved by methods such as: directly observing animals and their behaviour in situ; looking for signs of animals (eg tracks, dung); radar; thermal cameras; capture/mark/release of animals; or attaching or implanting monitoring devices (eg collars, leg bands, back packs or data loggers). Depending on the method of data collection the impact on the welfare of animals may be greater or less, both for the individual being monitored, and the population as a whole.
For example, to enable field biologists to monitor wild penguin populations, flipper bands may be used to mark individual penguins within a penguin colony. Although this practice is important for gathering population data, the welfare of individual banded penguins can be compromised when traditional metal bands are used and they may contribute to population decline over time. Metal bands cause increased drag whilst swimming (which in-turn can reduce swim speed and dive depth and impact on feeding), can snag on vegetation (causing injury), and may result in increased feather wear (leading to increased heat loss, an important consideration for birds that live in Antarctic conditions). Banded penguins have been shown to have a 16% higher mortality rate and produce 39% less chicks (Saraux et al, 2011).
When an identification or monitoring method affects animal welfare detrimentally, it is important to consider alternatives and in recognition of Dr Peter Barham’s and Bristol Zoo’s work on the welfare benefits of a new type of silicon flipper band which addressed many of the concerns of metal bands UFAW awarded them a UFAW Wild Animal Welfare Award. The silicon flipper band, designed by Dr Barham of Bristol University, and manufactured and tested by Bristol Zoo, was a simple and innovative design which was found to cause less feather wear and drag, and was also easier to read. Additionally, the flexible nature of rubber allowed the bands to expand if necessary, eg when the flipper expands during moult.
Another project which seeks to improve the welfare of wild animals fitted with external tags and supported by UFAW, is being carried out by Rory Wilson and his team who are investigating tag-use in free-ranging birds. Current guidelines state that devices should not exceed 3% of bird body mass – the aim being that the device does not detrimentally interfere with bird behaviour or welfare. However, according to Rory Wilson and his team this measurement is overly simplistic and does not take into account bird biology and lifestyle. The aim of their project is to develop a framework for assessing presumed physical tag detriment on birds (e.g. skin pressure, drag, predicted metabolic rate differences, moment arm effects) using physical principles which could be applied once the tag properties and the study species were known. A resultant generated ‘physical detriment matrix’ could then be used to give a more realistic assessment of detrimental tag effects.
Internal devices can also be important for monitoring animals and UFAW supported Mr James Macgregor’s work investigating platypus monitoring techniques (Murdoch University, Australia). In Australia wild platypuses are monitored in an effort to ensure their health and welfare, and to protect the population. However, current long-term monitoring methods involve either repeated capture or the application of relatively large tracking devices, both of which may adversely affect individual platypus welfare. Mr Macgregor wished to refine monitoring techniques through the use of an in-stream microchip reader which could monitor platypus movements and survival remotely and required only one capture of each platypus to implant the microchip. The study showed that in-stream microchips were an effective method for detecting microchipped platypus and Dr Macgregor believes that in-stream microchip readers will assist greatly in gathering new data and improving platypus welfare. The full results of Macgregor’s work were published in the Journal Pacific Conservation Biology.
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Live-trapping is another method which may be used during field studies. Live traps are designed to catch and hold the animal(s) of interest without harming them until the required details can be recorded by the field researcher. However, live-traps can compromise the welfare of animals, and some species will suffer more than others. Small mammals in particular may have a high accidental mortality rate – both due to their high metabolic rate (which means they cannot survive for long periods without sufficient and appropriate food and water) and their small size (which predisposes them to hypothermia in cold conditions).
However, sometimes simple and practical solutions can be found to such problems as discovered by Ms Randy Do (an Animal Welfare Student Scholar), who sought to address the high mortality rate when shrews are live-trapped (reported to be between 40 and 90%). Ms Do found that supplementing live-trap baits with mealworms reduced mortality rates by 49% and 64% for two types of vulnerable shrew and subsequently published her work in the Journal of Mammalogy (4).
Ms Do is one of over 350 young students that UFAW has supported via the UFAW Animal Welfare Student Scholarship scheme (previously the UFAW Vacation Scholarship Awards). This annual award, established in 1983, hopes to encourage and enable promising young students to develop their interests in animal welfare science by supporting them in carrying out their own research projects.
References
- Witmer GW. Wildlife population monitoring: some practical considerations. Wildlife Research. 32: 259-263. CSIRO Publishing.
- Saraux C, Le Bohec C, Durant JM, Viblanc VA, Gauthier-Clerc M, Beaune D, Park YH, Yoccoz NG, Stenseth NC, Le Maho Y. Letter: Reliability of flipper-banded penguins as indicators of climate change. Nature, 13 January 2011, V469. Doi:10.1038/nature09630.
- Macgregor JW, Holyoake CS, Munks S, Connolly JH, Robertson ID, Fleming PA and Warren KS. Novel use of in-stream microchip readers to monitor wild platypuses. Pacific Conservation Biology 20(4): 376–384. CSIRO Publishing. DOI: http://dx.doi.org/10.1071/PC140376.
- Do R, Shonfield J, McAdam AG. Reducing accidental shrew mortality associated with small-mammal livetrapping II: a field experiment with bait supplementation. Journal of Mammalogy. 94(4): 754-760. DOI: 10.1644/12-MAMM-A-242.1.
A selection of papers on monitoring wild animals published in the UFAW Journal, Animal Welfare:
Wilson RP, Sala JE, Gómez-Laich A, Ciancio J, Quintana F. 2015. Pushed to the limit: food abundance determines tag-induced harm in penguins. Animal Welfare. 24(1): 37-44. UFAW.
Cowan P, Forrester G, Warburton B. 2013. Short-term welfare implications of capture-mark-recapture trapping of medium-sized mammals: the brushtail possum (Trichosurus Vulpecula) as a case study. 22(4): 423-428. UFAW.
Serangeli MT, Cistrone L, Ancillotto L, Tomassini A, Russo D. 2012. The post-release fate of hand-reared orphaned bats: survival and habitat selection. Animal Welfare. 21(1): 9-18. UFAW.
Kelly A, Goodwin S, Grogan A, Mathews F. 2012. Further evidence for the post-release survival of hand-reared, orphaned bats based on radio-tracking and ring-return data. Animal Welfare. 21(1): 27-31. UFAWA.
Halstead C, Hunter D, Leighton K, Grogan A, Harris M. 2011. Factors affecting the likelihood of release of injured and orphaned woodpigeons (Columba palumbus). Animal Welfare. 20(4): 523-534. UFAW.
Wilson RP, Grogan A. 2011. Tags on seabirds: how seriously are instrument-induced behaviours considered? Animal Welfare. 20(4): 599-571. UFAW.
Swaisgood RR. 2010 The conservation-welfare nexus in reintroduction programmes: a role for sensory ecology. Animal Welfare. 19(2): 125-137. UFAW.
Wimberger K, Downs CT, Boyes RS. 2010. A Survey of wildlife rehabilitation in South Africa: is there a need for improved management? Animal Welfare. 19(4): 481-499. UFAW.
Kelly A, Goodwin S, Grogan A, Matthews F. 2008. Post-release survival of hand-reared pipistrelle bats (Pipistrellus spp). Animal Welfare. 17(4): 365-382. UFAW
Leighton K, Chilvers D, Charles A, Kelly A. 2008. Post-release survival of hand-reared tawny owls (Strix aluco) based on radio-tracking and leg band return data. Animal Welfare. 17(3): 207-214. UFAW.
Spencer KA, Harris S, Baker PJ, Cuthill IC. 2007. Song development in birds: the role of early experience and its potential effect on rehabilitation success. Animal Welfare. 16(1): 1-13. UFAW
Molony SE, Baker PJ, Garland L, Cuthill IC, Harris S. 2007. Factors that can be used to predict release rates for survival casualties. Animal Welfare. 16(3): 361-367. UFAW.
Reynolds JC. 2005. Trade-offs between welfare, conservation, utility and economics in wildlife management – a review of conflicts, compromises and regulation. Animal Welfare. 13(1): 133-138. UFAW.
Cooper EJ. 1998. Minimally invasive health monitoring of wildlife. Animal Welfare. 7(1): 35-44. UFAW.
Kirkwood JK, Sainsbury AW. 1996. Ethics of interventions for the welfare of free-living wild animals. Animal Welfare. 5(3): 235-243. UFAW.
Robertson CPJ, Harris S. 1995. The condition and survival after release of captive-reared fox cubs. Animal Welfare. 4(4): 281-294. UFAW.
Robertson CPJ, Harris S. 1995. The behaviour after release of captive-reared fox cubs. Animal Welfare. 4(4): 295-306. UFAW.
Morrist PA, Meakin K, Sharafi S. 1993. The behaviour and survival of rehabilitated hedgehogs (Erinaceus europaeus). Animal Welfare. 2(1): 53-66. UFAW.
