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Apex carnivores are wide-ranging, low-density, hard to detect, and declining throughout most of their range, making population monitoring both critical and challenging. Rapid and inexpensive index calibration survey (ICS) methods have been developed to monitor large African carnivores. ICS methods assume constant detection probability and a predictable relationship between the index and the actual population of interest. The precision and utility of the resulting estimates from ICS methods have been questioned. We assessed the performance of one ICS method for large carnivores-track counts-with data from two long-term studies of African lion populations. We conducted Monte Carlo simulation of intersections between transects (road segments) and lion movement paths (from GPS collar data) at varying survey intensities. Then, using the track count method we estimated population size and its confidence limits. We found that estimates either overstate precision or are too imprecise to be meaningful. Overstated precision stemmed from discarding the variance from population estimates when developing the method and from treating the conversion from tracks counts to population density as a back-transformation, rather than applying the equation for the variance of a linear function. To effectively assess the status of species, the IUCN has set guidelines, and these should be integrated in survey designs. We propose reporting the half relative confidence interval width (HRCIW) as an easily calculable and interpretable measure of precision. We show that track counts do not adhere to IUCN criteria, and we argue that ICS methods for wide-ranging low-density species are unlikely to meet those criteria. Established, intensive methods lead to precise estimates, but some new approaches, like short, intensive, (spatial) capture-mark-recapture (CMR/SECR) studies, aided by camera trapping and/or genetic identification of individuals, hold promise. A handbook of best practices in monitoring populations of apex carnivores is strongly recommended.
Egil Dröge; Scott Creel; Matthew S. Becker; Andrew J. Loveridge; Lara L. Sousa; David W. Macdonald. Assessing the performance of index calibration survey methods to monitor populations of wide‐ranging low‐density carnivores. Ecology and Evolution 2020, 10, 3276 -3292.
AMA StyleEgil Dröge, Scott Creel, Matthew S. Becker, Andrew J. Loveridge, Lara L. Sousa, David W. Macdonald. Assessing the performance of index calibration survey methods to monitor populations of wide‐ranging low‐density carnivores. Ecology and Evolution. 2020; 10 (7):3276-3292.
Chicago/Turabian StyleEgil Dröge; Scott Creel; Matthew S. Becker; Andrew J. Loveridge; Lara L. Sousa; David W. Macdonald. 2020. "Assessing the performance of index calibration survey methods to monitor populations of wide‐ranging low‐density carnivores." Ecology and Evolution 10, no. 7: 3276-3292.
Human activity affecting the welfare of wild vertebrates, widely accepted to be sentient, and therefore deserving of moral concern, is widespread. A variety of motives lead to the killing of individual wild animals. These include to provide food, to protect stock and other human interests, and also for sport. The acceptability of such killing is widely believed to vary with the motive and method. Individual vertebrates are also killed by conservationists. Whether securing conservation goals is an adequate reason for such killing has recently been challenged. Conventional conservation practice has tended to prioritise ecological collectives, such as populations and species, when their interests conflict with those of individuals. Supporters of the ‘Compassionate Conservation’ movement argue both that conservationists have neglected animal welfare when such conflicts arise and that no killing for conservation is justified. We counter that conservationists increasingly seek to adhere to high standards of welfare, and that the extreme position advocated by some supporters of ‘Compassionate Conservation’, rooted in virtue ethics, would, if widely accepted, lead to considerable negative effects for conservation. Conservation practice cannot afford to neglect consequences. Moreover, the do-no-harm maxim does not always lead to better outcomes for animal welfare.
Paul J. Johnson; Vanessa M. Adams; Doug P. Armstrong; Sandra E. Baker; Duan Biggs; Luigi Boitani; Alayne Cotterill; Emma Dale; Holly O’Donnell; Armstrong Doug; Egil Droge; John G. Ewen; Ruth E. Feber; Piero Genovesi; Clive Hambler; Bart J. Harmsen; Lauren A. Harrington; Amy Hinks; Joelene Hughes; Lydia Katsis; Andrew Loveridge; Axel Moehrenschlager; Christopher O’Kane; Meshach Pierre; Steve Redpath; Lovemore Sibanda; Pritpal Soorae; Mark Stanley Price; Peter Tyrrell; Alexandra Zimmermann; Amy Dickman. Consequences Matter: Compassion in Conservation Means Caring for Individuals, Populations and Species. Animals 2019, 9, 1115 .
AMA StylePaul J. Johnson, Vanessa M. Adams, Doug P. Armstrong, Sandra E. Baker, Duan Biggs, Luigi Boitani, Alayne Cotterill, Emma Dale, Holly O’Donnell, Armstrong Doug, Egil Droge, John G. Ewen, Ruth E. Feber, Piero Genovesi, Clive Hambler, Bart J. Harmsen, Lauren A. Harrington, Amy Hinks, Joelene Hughes, Lydia Katsis, Andrew Loveridge, Axel Moehrenschlager, Christopher O’Kane, Meshach Pierre, Steve Redpath, Lovemore Sibanda, Pritpal Soorae, Mark Stanley Price, Peter Tyrrell, Alexandra Zimmermann, Amy Dickman. Consequences Matter: Compassion in Conservation Means Caring for Individuals, Populations and Species. Animals. 2019; 9 (12):1115.
Chicago/Turabian StylePaul J. Johnson; Vanessa M. Adams; Doug P. Armstrong; Sandra E. Baker; Duan Biggs; Luigi Boitani; Alayne Cotterill; Emma Dale; Holly O’Donnell; Armstrong Doug; Egil Droge; John G. Ewen; Ruth E. Feber; Piero Genovesi; Clive Hambler; Bart J. Harmsen; Lauren A. Harrington; Amy Hinks; Joelene Hughes; Lydia Katsis; Andrew Loveridge; Axel Moehrenschlager; Christopher O’Kane; Meshach Pierre; Steve Redpath; Lovemore Sibanda; Pritpal Soorae; Mark Stanley Price; Peter Tyrrell; Alexandra Zimmermann; Amy Dickman. 2019. "Consequences Matter: Compassion in Conservation Means Caring for Individuals, Populations and Species." Animals 9, no. 12: 1115.
Many studies have shown that behavioral responses to the risk posed by predators can carry costs for prey by reducing fecundity or survival, with consequent effects on population dynamics. Responses to risk include increased vigilance and reduced foraging, movement to safe habitats, increases or decreases in group size, and changes in patterns of movement. While we know that prey can detect and respond to both long term (LT) and short term (ST) variation in risk, field studies have only recently begun to consider how these responses might differ. Here, we hypothesize that prey movement patterns should respond differently to cues of LT and ST variation in risk. Specifically, cues of elevated LT risk might lead to decreased movement to improve the assessment of ST risk, while elevated ST risk might favor increased movement to reduce the proximity or duration of risks that are already assessed to be acute. We further hypothesize that decreases in movement are likely to be a general response to LT risk, while responses to ST risk are likely to vary in a manner that depends on the type of predator. In Liuwa Plain National Park, we found that wildebeest movements responded to the local intensity of predator use (LT risk), after controlling for other seasonal, diurnal and bottom-up effects. Speed decreased considerably and turning angles increased considerably, combining to markedly decrease linear movements. In contrast, immediate encounters with predators (ST risk) typically provoked fast, linear flight, and this effect was stronger for encounters with coursing predators. The effect of long term risk was to cause wildebeest to move more slowly and less linearly, i.e. to slow down and turn around, as part of a suite of behavioral responses, which also includes increased vigilance, that promote cautious assessment of ST risks when in locations with high levels of LT risk. This result has broad implications of understanding the influence of predation risk on foraging patterns of ungulates as this relationship is much more complex than simple avoidance of areas of ‘high risk’.
Egil Dröge; Scott Creel; Matthew Becker; David Christianson; Jassiel M'Soka; Fred Watson. Response of wildebeest (Connochaetes taurinus) movements to spatial variation in long term risks from a complete predator guild. Biological Conservation 2019, 233, 139 -151.
AMA StyleEgil Dröge, Scott Creel, Matthew Becker, David Christianson, Jassiel M'Soka, Fred Watson. Response of wildebeest (Connochaetes taurinus) movements to spatial variation in long term risks from a complete predator guild. Biological Conservation. 2019; 233 ():139-151.
Chicago/Turabian StyleEgil Dröge; Scott Creel; Matthew Becker; David Christianson; Jassiel M'Soka; Fred Watson. 2019. "Response of wildebeest (Connochaetes taurinus) movements to spatial variation in long term risks from a complete predator guild." Biological Conservation 233, no. : 139-151.
Both short-term and long-term variation in predation risk can affect the behaviour of prey, thus affecting growth, reproduction, survival and population dynamics. Inferences about the strength of such ‘risk effects’ in the wild have been limited by a lack of studies that relate antipredator responses to the magnitude of direct predation, measure responses of prey to risk from complete predator guilds, and quantify risk in more than one way. Here, we quantify behavioural responses of a complete ungulate prey guild to long-term and short-term variation in risks from all of the large predators in Liuwa Plain National Park, with known patterns of direct predation. Our analysis allows the first direct test for interaction between responses to long-term and short-term risk in the wild, and reveals that prey vigilance responds strongly to locations with high long-term risk when short-term risk is high, but not when short-term risk is low. This result has broad ramifications for the design and interpretation of field studies of antipredator behaviour, its costs and its consequences for population dynamics.
Egil Dröge; Scott Creel; Matthew S. Becker; Jassiel M’Soka. Risky times and risky places interact to affect prey behaviour. Nature Ecology & Evolution 2017, 1, 1123 -1128.
AMA StyleEgil Dröge, Scott Creel, Matthew S. Becker, Jassiel M’Soka. Risky times and risky places interact to affect prey behaviour. Nature Ecology & Evolution. 2017; 1 (8):1123-1128.
Chicago/Turabian StyleEgil Dröge; Scott Creel; Matthew S. Becker; Jassiel M’Soka. 2017. "Risky times and risky places interact to affect prey behaviour." Nature Ecology & Evolution 1, no. 8: 1123-1128.