Effects of Long-Term Hunting on Group Size in the African Lion (Panthera Leo) and African Wild Dog (Lycaon Pictus).
Emily O’Regan
Hypotheses
• Long-term hunting has resulted in a selection pressure, favouring smaller group sizes.
• This selection pressure has caused behavioural changes. Methods
• Meta-analysis
• Historic data and recent data
• English, Dutch, Afrikaans and Portuguese literature 50
45 R² = 0.18 40
35
30
25
20 Lion Pride Size Pride Lion 15
10
5
0 1820 1840 1860 1880 1900 1920 1940 1960 1980 2000 2020 Year Figure 1. Linear regression model showing African lion (Panthera leo) pride sizes across Africa, from 1830 to 1997 for all data (r2 = 0.180, n = 71, p ≤ 0.001; y = -0.1442x + 298.4). 30
25
20
15
10 Mean Lion Pride Size Pride Lion Mean
5
0 1830 - 1911 1950-1997 Year Figure 2. Bar chart showing mean size of African lion (Panthera leo) prides between 1830-1911 (20.91) and 1950-1997 (14.71).
120
r² = 0.53
100
80
60
Group Size Group Dog Dog
40 Wild Wild
20
0 1880 1900 1920 1940 1960 1980 2000 2020 Year
Figure 3. Linear regression model showing African wild dog (Lycaon pictus) pack sizes across Africa, from 1900 to 2009 (r2 = 0.53, n = 107, p ≤ 0.001; y = -0.5624x + 1124.2). 70
60
50
40
30
20
Mean Wild Dog Pack Size Pack Dog Wild Mean 10
0 Pre-1960 1960-2015 Year
Figure 4. Bar chart showing mean size of African wild dog (Lycaon pictus) packs pre-1960 (57.5) and 1960-2015 (9.8).
Smaller prides Figure 5. Feedback loop showing the implications for lion ecology, are governed with regard to declining pride size and the effect of infanticide. by smaller coalitions
Smaller Large-scale coalitions are decline of lion less able to population repel invaders
Rate of Greater infanticide is turnover of lion increased coalitions
Example – Spotted Hyena
12 200 180 10
160
140 8 120 6 100 Hyena Group Size 80 Prey Body Mass (Kg) 4
60 Hyena Group Size Group Hyena
40 (Kg) Mass Body Prey 2 20 0 0 Zebra Wildebeest Gazelle Prey Species Figure 6. Mean number of hyenas (Crocuta crocuta) in a hunting group, for three different prey species of varying body mass. (Adapted from Kruuk, 1972; Hayward and Kerley 2005.) Shifting Baseline
• The shifting baseline syndrome of fisheries (Pauly, 1995).
• Gradual accommodation of reduced populations.
• Group size and behaviour? “Until lions have their historians, tales of the hunt shall always glorify the hunter.” - African Proverb
Emily O’Regan [email protected] References
• Kruuk, H. (1972). The Spotted Hyena. Chicago: University of Chicago Press.
• Hayward, M.W. and Kerley, G.I. (2005). Prey preferences of the lion (Panthera leo). Journal of zoology, 267(3), pp.309-322.
• Loveridge, A.J., Searle, A.W., Murindagomo, F. and Macdonald, D.W. (2007). The impact of sport-hunting on the population dynamics of an African lion population in a protected area. Biological Conservation,134(4), pp.548-558.
• Milner, J.M., Nilsen, E.B. and Andreassen, H.P. (2007). Demographic side effects of selective hunting in ungulates and carnivores. Conservation biology, 21(1), pp.36-47.
• Pauly, D. (1995). Anecdotes and the shifting baseline syndrome of fisheries. Trends in ecology and evolution, 10(10), p.430.
• Courchamp, F. and Macdonald, D.W. (2001). Crucial importance of pack size in the African wild dog Lycaon pictus. Animal Conservation, 4(2), pp.169-174.