Trends in Ecology & Evolution
OpinionEndangered species and a threatened discipline: behavioural ecology
Section snippets
Behavioural ecology under threat
Most biologists realize that we are living in an extraordinary period, a time of mass extinction caused by humans. Population growth and increased per capita demands on resources are the root causes, resulting in over-exploitation, habitat alterations, climate change, invasions by non-native species, and pollution 1, 2. Biologists from many different subdisciplines have recently sought to link these changes to their own scientific specialties, including life histories 3, 4, migration patterns
Species loss
Loss of species is particularly significant for behavioural ecologists because behaviour leaves no fossil record. When a species goes extinct, its behaviour can be inferred only indirectly. We will never know how the dodo Raphus cucullatus foraged, the significance of the remarkable sexual dimorphism in bill structure of the New Zealand huia Heteralocha acutirostris, whether golden toads Bufo periglenes exhibited behavioural syndromes, or if Tasmanian wolves Thylacinus cynocephalus had
Invasive species
Invasive species often prey on or compete with native flora and fauna [50]. Humans have introduced invasive species purposely or inadvertently, and have created opportunities for dispersive invaders to settle by altering native habitats. As a result, native species will progressively live in environments permeated with invasives.
There are many examples of invasive species altering the community structure of native species, such as introduced fishes in California river systems [51], and cane
Loss of habitats generally
Loss of habitats not only eliminates or confines populations that depend on them, but also affects our ability to understand the breadth of behavioural responses to different environments. This can occur at different spatial scales: across large biomes such as Madagascar, the Hawaiian Islands, and the Caribbean Islands, and also at smaller scales. For example, in some species, helpers-at-the-nest are found only in saturated habitats (e.g. Seychelles warblers Acrocephalus sechellensis [59]). If
Pollution
Environmental pollution affects morphology, physiology and behaviour in many ways. For example, chemical pollution feminizes amphibians [65] and affects vertebrate sexual orientation and homosexuality [66]. Environmental disturbance affects signaling and sexual ornamentation. In urban settings behavioural ecologists’ studies of sexual selection in birds will be obfuscated when females are unable to choose mates based on songs because low frequency traffic noise alters sound transmission 67, 68.
Climate change
There is a growing body of literature on the effects of global warming on geographic ranges [70] and aspects of behaviour that include migration [71] and breeding dates [5] of birds and mammals [72]. In addition, changes in the distribution, abundance, and phenology of important plant resources will probably have effects on ranging, grouping behaviour and intra- and interspecific competition. Some of these behavioural characteristics will change faster than others, resulting in a heterogeneous
Increased human contact
Contact with humans changes the behaviour of wild species. Some show great wariness initially, whereas others are almost naïve in their responses; subsequently, some species habituate and others remain fearful. As a consequence, some become commensals such as Virginia opossums Didelphis virginiana, raccoons, coyotes Canis latrans, striped skunks Mephitis mephitis, and white-tailed deer Odocoileus virginianus, whereas others become more shy and reclusive, such as spotted skunks Spilogale gracilis
Conclusion
In a world that is patently disturbed, and as pristine environments that could serve as scientific baselines disappear, it will be increasingly difficult for behavioural ecologists to determine which behaviours are adaptive and which anachronistic. This obstructs analyses of the reproductive costs and benefits, and thus the fitness consequences, of behavioural variants: an essential goal of behavioural ecologists. Similar problems have long bedeviled evolutionary anthropology [73] and are being
Acknowledgements
We thank John Alcock, Dan Blumstein, John Eadie, Geoff Hill, John Hoogland, Andy Marshall, Mike Ryan, Janet Shellman Sherman, David Westneat, and two anonymous reviewers for discussion or comments.
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