Background. Vigilance in African mammalian carnivores. Antipredator behaviors: 1. Avoid detection. Undergrad: McGill University Dr.

Transcription

1 Vigilance in African mammalian carnivores Background Undergrad: McGill University Dr. Kramer s lab Ph.D.: MSU Dr. Holekamp s lab Wiline Trouilloud Photo: Jaime Tanner Antipredator behaviors: 1. Avoid detection Cryptic behaviors: Ex: Slow down; freeze; body decorations Habitat selection: Ex: Under cover; in the open; dark water Vigilance Join groups (conspecifics or polyspecifics)

2 Antipredator behaviors: 2. Once detected Warn predator that it s detected Alarm others Flight (run) Fight (spray, etc) Escape by losing body parts Mob predator Play dead Components of vigilance Duration of head raise (in sec) Rate of head raises (#/min) = Percent time spent vigilant Vigilance is a behavior that increases the probability of detecting a stimulus Today: only rate

3 Underlying theory Behavior should optimize fitness Fitness = related to birth/death Classical studies Here, we re assessing fitness by looking at growth (i.e. food intake; rest; parental care) Foraging: Tradeoff between vigilance and food intake Outline of research Nothing on carnivores! Comparative study on mammalian carnivores Case study of spotted hyenas Background on the project Natural history of the spotted hyena Description of vigilance in hyenas Experiments (playbacks) in hyenas

4 Comparative study of vigilance in African carnivores Background on study Need to understand behavior to protect species esp. anti-predator behavior Predictions: Species with larger body sizes will have lower rates of vigilance Species more social will have lower rates of vigilance Methodology 11 Context: feeding and resting Video + independent variables Sympatric species Range of body sizes to test predictions Body weight (kg) Photo: Kay Holekamp

5 1 Vigilance while feeding Vigilance while feeding Rate of head raises (#/min) Rate of head raises (#/min) Regression: R2=.26 F1,216 = 5.92 P=.1 Dwarf mg Band mg Jackal Wild dog Lion Lion Cheet. Leop. Hyena Sociality Index F M Body weight 1.2 Vigilance while resting Conclusions Rate of vigilance (#/min) Much lower rate of vigilance while resting (what would you predict for duration?) Decrease rate of vigilance with increasing body weight When feeding: social species have higher rate of vigilance. Cheetah Hyena Lion F Lion M Conflicting factors: phylogeny, habitat, age, # predators Body weight

6 Now one species more in depth Spotted hyenas (Crocuta crocuta) Social clan (up to 1 individuals) Why hyenas? Kill sequence (Predator~6kg; Prey~18kg) Intense intraspecific competition Photo: Kay Holekamp Ph t J S ith

7 Intense interspecific competition Hyena Project Dr. Holekamp s lab Vigilance of a social carnivore Predictions Photo: Holekamp Lab Should hyenas be more vigilant when young or as adults? Should hyena mothers be more worried about cubs when really young or when older? Description of vigilance in a social carnivore Variation with rank, age, contexts Group size effect? Predictions: Hyenas will be most vigilant when they are the most at risk (i.e. when being weaned) Mothers will be most vigilant when cubs are young

8 Effects of age on the rate of vigilance for hyenas feeding on kills Effect of age on rate of vigilance for hyenas resting Photo: Katy Califf # head raises / min F 1,36 =2.9 r 2 =.37 P< Age (months) # head ups / min Age (in months) F2,31=8.7; r2=.35; P=.1 Effect of age of litter on rate of vigilance for mothers nursing Photo: Kay Holekamp Relationship between lions and hyenas Adult females' rates of vigilance while nursing a litter (#/min) 3.5 N=22 R 2 =.317 P< Age (in months) of the litter being nursed Playback experiments of lion roars to hyenas of different age and rank Hypothesis: Low rank and low prey availability will lead to an increased risk taking, esp. in newly weaned hyenas

9 Methodology Effect of age on the proportion of time spent fleeing away from speakers following a lion roar playback 1 m Proportion of time spent fleeing away from speakers 1 N=25 R=.65 P= Age (in months) Rate of movement following playback Proportion time spent approaching, fleeing or orienting towards the speakers after roar playback Rate of movement (m/min) * 5 8 ** 5 Roar Wahoo ** Percent time spent (%) Approaching Fleeing Orienting 8 NS P=.6 13 NS cub subadult adult Cubs class 3 Subadults class Adults class 5

10 Human disturbance and its effects on antipredator behavior Study populations Mara River KENYA Compare clan with low disturbance to clan with high disturbance Mara River Clan Talek River Talek Clan Major Rivers Reserve Border Mara River Territory Boundary Talek Territory Boundary W N E Kilometers S Figure 1. Map of Masai Mara National Reserve and estimated territory boundaries of the Mara River and Talek spotted hyena clans. Photos: Joe Kolowski Study 1: Observations of vigilance in all 3 contexts (feeding, resting, nursing) for both clans Study 2: Playback experiments of cow bells (control sound: church bells) Cow bells Church bells Conclusions Young hyenas less vigilant than adults (both when resting and when feeding) Mothers most vigilant when nursing young cubs Young cubs show stronger reactions to lion roars than adults (spend more time fleeing, flee faster)

11 Acknowledgements 1 Vigilance while feeding Funding: AAUW International fellowship, Barnett-Rosenberg fellowship, Graduate Women in Sciences Eloise-Gerry grant, EEBB, Department of Zoology, College of Natural Sciences, NSF to KEH. Audrey DeRose-Wilson and Aimee Cokayne in the field Average duration of head raises (in sec) Dr. Holekamp and the Holekamp lab Dwarf mg Band mg Jackal Wild dog Cheet. Leop. Hyena Lion F Lion M Body weight 5 Vigilance while resting Duration of head raises (in sec) cheetah hyena lion F lion M X Data Body weight