Goodheart Ben, Creel Scott, Vinks Milan A, Banda Kambwiri, Reyes de Merkle Johnathan, Kusler Anna, Dart Chase, Banda Kachama, Becker Matthew S, Indala Peter, Simukonda Chuma, Kaluka Adrian
Department of Ecology, Montana State University, 310 Lewis Hall, Bozeman, MT, 59717, USA.
Zambian Carnivore Programme, PO Box 80, Mfuwe, Eastern Province, Zambia.
Mov Ecol. 2022 Mar 31;10(1):16. doi: 10.1186/s40462-022-00316-7.
Prey depletion is a threat to the world's large carnivores, and is likely to affect subordinate competitors within the large carnivore guild disproportionately. African lions limit African wild dog populations through interference competition and intraguild predation. When lion density is reduced as a result of prey depletion, wild dogs are not competitively released, and their population density remains low. Research examining distributions has demonstrated spatial avoidance of lions by wild dogs, but the effects of lions on patterns of movement have not been tested. Movement is one of the most energetically costly activities for many species and is particularly costly for cursorial hunters like wild dogs. Therefore, testing how top-down, bottom-up, and anthropogenic variables affect movement patterns can provide insight into mechanisms that limit wild dogs (and other subordinate competitors) in resource-depleted ecosystems.
We measured movement rates using the motion variance from dynamic Brownian Bridge Movement Models (dBBMMs) fit to data from GPS-collared wild dogs, then used a generalized linear model to test for effects on movement of predation risk from lions, predictors of prey density, and anthropogenic and seasonal variables.
Wild dogs proactively reduced movement in areas with high lion density, but reactively increased movement when lions were immediately nearby. Predictors of prey density had consistently weaker effects on movement than lions did, but movements were reduced in the wet season and when dependent offspring were present.
Wild dogs alter their patterns of movement in response to lions in ways that are likely to have important energetic consequences. Our results support the recent suggestion that competitive limitation of wild dogs by lions remains strong in ecosystems where lion and wild dog densities are both low as a result of anthropogenic prey depletion. Our results reinforce an emerging pattern that movements often show contrasting responses to long-term and short-term variation in predation risk.
猎物数量减少对全球大型食肉动物构成威胁，且可能对大型食肉动物群落中的从属竞争者产生不成比例的影响。非洲狮通过干扰竞争和种内捕食限制非洲野犬的数量。当由于猎物数量减少导致狮子密度降低时，野犬并不会因竞争压力减轻而数量增加，其种群密度依然很低。研究分布情况的研究表明，野犬在空间上会避开狮子，但狮子对野犬运动模式的影响尚未得到验证。对于许多物种而言，运动是能量消耗最大的活动之一，对于像野犬这样的奔跑型猎手来说尤其如此。因此，研究自上而下、自下而上和人为因素如何影响运动模式，有助于深入了解在资源匮乏的生态系统中限制野犬（以及其他从属竞争者）数量的机制。
我们使用拟合GPS项圈野犬数据的动态布朗桥运动模型（dBBMMs）中的运动方差来测量运动速率，然后使用广义线性模型来检验狮子的捕食风险、猎物密度预测因子、人为因素和季节变量对运动的影响。
野犬会主动减少在狮子密度高的区域的活动，但当狮子就在附近时会被动增加活动。猎物密度预测因子对运动的影响始终比狮子的影响弱，但在雨季和有依赖后代时活动会减少。
野犬会根据狮子的情况改变其运动模式，这可能会产生重要的能量学后果。我们的研究结果支持了最近的一项观点，即在由于人为猎物减少导致狮子和野犬密度都很低的生态系统中，狮子对野犬的竞争限制仍然很强。我们的研究结果强化了一种新出现的模式，即运动通常对捕食风险的长期和短期变化表现出不同的反应。
