BIOS 6150: Ecology Dr. Stephen Malcolm, Department of Biological Sciences Week 6: Predation and predatory behavior: Lecture summary: Nature of predation. Diet breadth & choice. Optimal foraging. Functional responses Mutual interference. Aggregative response. Marginal value theorem. J. Kobalenko. 1997. Forest Cats Of North America. Firefly Books Snowshoe hare and lynx. http://www.americazoo.com/goto/ index/mammals/134.htm BIOS 6150: Ecology - Dr. S. Malcolm. Week 6: Predation and predatory behavior Slide - 1
2. Predation: Is a description of the interaction between predator foraging behavior and prey defense. This includes both behavior and population dynamics. Fig. 20.1 from Malcolm (1992) in Natural Enemies edited by M.J. Crawley (Blackwell). BIOS 6150: Ecology - Dr. S. Malcolm. Week 6: Predation and predatory behavior Slide - 2
3. Predation literature: Very strong emphasis on predator foraging behavior and prey-predator dynamics. Defense is mostly relegated to the realms of natural history description. Predator foraging behavior is a description of: where they feed. what they feed on. how they are influenced by other predators. how they are influenced by prey density. BIOS 6150: Ecology - Dr. S. Malcolm. Week 6: Predation and predatory behavior Slide - 3
4. Diet composition and food preference: Predators can be: Monophagous: single prey type and have a large impact on prey population dynamics Oligophagous: few prey types, or, Polyphagous: many prey types and probably have little impact on the population dynamics of any one species. BIOS 6150: Ecology - Dr. S. Malcolm. Week 6: Predation and predatory behavior Slide - 4
5. Prey choice: Within different diet breadths predators choose more profitable prey preferentially (Table 9.1) and so food can also be assessed by predators as either: Ranked food resources that are most valuable or perfectly substitutable see Figs. 9.14 and 9.15, or, Balanced food resources that are integral or complementary Usually necessary to balance required nutrients that may be absent from high ranked foods. BIOS 6150: Ecology - Dr. S. Malcolm. Week 6: Predation and predatory behavior Slide - 5
6. Switching: Predators can also switch their food preference as in Fig. 9.15: Perhaps through learned abilities to handle prey more profitably: More efficient balance among search, pursuit, and handling behaviors before consumption: This may be facilitated by specific search images. Such changes in diet may also be seasonal or on shorter time scales that may be associated with the induction of physiologies better suited to exploiting the food resource. BIOS 6150: Ecology - Dr. S. Malcolm. Week 6: Predation and predatory behavior Slide - 6
7. Optimal foraging and diet width: Why are real diets "narrower" than potential diets? If energy maximization is the primary criterion that correlates well with fitness then optimal foraging theory is useful. MacArthur & Pianka (1966) initiated the influential optimal foraging theory approach for the description of the evolutionary ecology of predatory behavior based on: Maximization of the net rate of energy intake: gross energy intake - energetic costs of obtaining that energy. Predators incur energy and time costs of: Searching for prey Handling prey: Includes: detection, pursuit, acceptance, subjugation & consumption BIOS 6150: Ecology - Dr. S. Malcolm. Week 6: Predation and predatory behavior Slide - 7
8. Optimal foraging theory: The aim is to predict the expected foraging strategy under specified conditions (Fig. 9.17): Is it a tactic or a strategy? Generalist costs: Low time search costs but higher costs of handling both unprofitable and profitable prey. Specialist costs: High time costs but lower costs of handling profitable prey. BIOS 6150: Ecology - Dr. S. Malcolm. Week 6: Predation and predatory behavior Slide - 8
9. Diet profitability: MacArthur & Pianka argued that a prey item ( i ) should be included (and diet width expanded) if it is equal to, or more profitable than, the average profitability of the present diet, thus if: E i /h i E/(s + h) where i is the next most profitable prey item E = energy content h = handling time (therefore E/h = profitability) s = search time BIOS 6150: Ecology - Dr. S. Malcolm. Week 6: Predation and predatory behavior Slide - 9
10. Foraging guilds: Handling time < search time = generalists: e.g. foliage gleaning bird guild: A guild is a group of individuals that exploit the same resource in the same way (after Root). Handling time > search time = specialists: e.g. lions living near prey: Note: handling time includes pursuit time! See text these don t make sense to me, despite discussing this with Mike Begon! BIOS 6150: Ecology - Dr. S. Malcolm. Week 6: Predation and predatory behavior Slide - 10
11. Foraging constraints: Abiotic and Biotic: More dimensions of realized niches! Biotic: see Figures 9.18 and 9.19 Abiotic: e.g. the interaction between temperature and oxygen constrains Notonecta foraging for submerged or floating prey according to dissolved oxygen levels (see Figs 2 & 4 from Cockrell (1984) Journal of Animal Ecology 53(2): 519-532.) BIOS 6150: Ecology - Dr. S. Malcolm. Week 6: Predation and predatory behavior Slide - 11
12. Functional Responses: Describe the relationship between an individual predator s consumption rate and prey density: After Solomon (1949) but developed by Holling (1959). 3 kinds recognized by Holling: Type 1 (linear). Type 2 (asymptotic). Type 3 (sigmoid). BIOS 6150: Ecology - Dr. S. Malcolm. Week 6: Predation and predatory behavior Slide - 12
13. Type 2 Functional Response: Type 2 functional response is most frequently observed (see Figs 10.9 & 9.7): Handling t stays constant but search t decreases with increasing prey density. Thus total handling time increases. Handling time T h determines the height of the curve plateau. Attack rate a determines rate that plateau is reached. BIOS 6150: Ecology - Dr. S. Malcolm. Week 6: Predation and predatory behavior Slide - 13
14. Types 1 & 3 Functional Responses: Type 1 functional response (slope = a) as in filter-feeding Daphnia (Fig. 10.8). Type 3 functional responses as in vertebrate predators capable of learning (Fig. 10.10) and showing switching behaviors: Increased attack rate and increased searching time or decreased handling time. BIOS 6150: Ecology - Dr. S. Malcolm. Week 6: Predation and predatory behavior Slide - 14
15. Holling's disc equation: The functional response relationship is described by Holling's disc equation in which: Prey eaten, P e = a T s N where T s is the period of searching time during which P e prey are eaten, and N = prey density but, T s = T - T h P e where T = total time and so, P e = a (T - T h P e )N Y = a(t - by)x, in Tostowaryk (1972) or, rearranging, P e = ant/1 + at h N BIOS 6150: Ecology - Dr. S. Malcolm. Week 6: Predation and predatory behavior Slide - 15
16. Michaelis-Menten-Holling equation: Holling s disc equation is the same as the continuous form: b(n) = mn/(w + N), where m is the maximum predator attack rate, b = rate of change of N due to the interaction, and, w is prey density where attack rate is half saturated. This is also the same as the Michaelis-Menten equation that describes the kinetics of enzyme catalyzed reactions: v o = V max S/K m + S, where, K m = w, S = N, V max = m BIOS 6150: Ecology - Dr. S. Malcolm. Week 6: Predation and predatory behavior Slide - 16
17. Effects of functional responses on population dynamics: 1) Decelerating consumption rate results in destabilization because it is inversely density dependent: All 3 functional responses at high density. 2) Accelerating consumption rate results in density-dependent stabilization: Type 3 functional response at low density. BIOS 6150: Ecology - Dr. S. Malcolm. Week 6: Predation and predatory behavior Slide - 17
18. Predator density - mutual interference: Mutual interference - effects of competition: Effects of territoriality, or resource defense, or direct interference competition, or indirect exploitative competition, can all increase with increased predator density: Figure 9.10 shows density dependent changes when searching efficiency a (=attack rate) is plotted against predator density: The slope of this relationship m is the coefficient of interference. This negative slope tends to stabilize predatorprey dynamics. In contrast to social facilitation at low predator density: e.g. foraging dolphins. BIOS 6150: Ecology - Dr. S. Malcolm. Week 6: Predation and predatory behavior Slide - 18
19. Prey density - aggregative responses by predators to prey patches : Aggregative response Predators spend more time in high density prey patches than low density patches (where spatial distribution varies) (Fig. 9.11). Combined functional and aggregative responses (Fig. 9.22). Impact on population dynamics: Partial prey refuges at both high and low prey density: Lowered probability of attack tends to stabilize predator-prey population dynamics (Fig. 5.19) BIOS 6150: Ecology - Dr. S. Malcolm. Week 6: Predation and predatory behavior Slide - 19
20. The ideal free distribution of predators and prey: Aggregation + interference may combine to generate: An ideal free distribution (Fig. 9.27), or, Patchiness in time and space can generate stability: As in Huffaker's orange+mites experiment: Through equal ( ideal ) patch profitabilities after ( free ) redistribution. Interaction between competition and predation! BIOS 6150: Ecology - Dr. S. Malcolm. Week 6: Predation and predatory behavior Slide - 20
21. The Marginal Value Theorem: Based on the work of Charnov (1976) and Parker & Stuart (1976) to predict the behavior of an optimal forager in patches of food of different profitabilities: The forager should maximize its overall intake of a resource (energy) per time spent foraging in habitats with food distributed patchily: How long should the forager spend in patches of varying profitability? Fig. 9.22 illustrates the model and Fig. 9.23 is a test of the model (Cowie). BIOS 6150: Ecology - Dr. S. Malcolm. Week 6: Predation and predatory behavior Slide - 21
Table 9.1 (3 rd ed.): BIOS 6150: Ecology - Dr. S. Malcolm. Week 6: Predation and predatory behavior Slide - 22
Figure 9.14: Selection of the most profitable prey by crabs and wagtails BIOS 6150: Ecology - Dr. S. Malcolm. Week 6: Predation and predatory behavior Slide - 23
Figure 9.15: Preference (a & c), switching (b) and switching + learning (d & e) BIOS 6150: Ecology - Dr. S. Malcolm. Week 6: Predation and predatory behavior Slide - 24
Figure 9.17: Predictions and observations of diet choice in great tits and bluegill sunfish BIOS 6150: Ecology - Dr. S. Malcolm. Week 6: Predation and predatory behavior Slide - 25
Figure 9.18: Seasonal variation in predicted and observed habitat profitabilities for bluegill sunfish. BIOS 6150: Ecology - Dr. S. Malcolm. Week 6: Predation and predatory behavior Slide - 26
Figure 9.19: Effect of largemouth bass on sunfish feeding distribution. BIOS 6150: Ecology - Dr. S. Malcolm. Week 6: Predation and predatory behavior Slide - 27
Figure 2: Effect of water temperature on time spent submerged by foraging Notonecta (Cockrell, 1984): Journal of Animal Ecology 53(2): 519-532.) BIOS 6150: Ecology - Dr. S. Malcolm. Week 6: Predation and predatory behavior Slide - 28
Figure 4: Mean length of time spent submerged by Notonecta and number of attacks on flies at the surface and Asellus on the bottom of water tanks at 3 dissolved oxygen concentrations. Cockrell, B.J. 1984. Journal of Animal Ecology 53(2): 519-532.) BIOS 6150: Ecology - Dr. S. Malcolm. Week 6: Predation and predatory behavior Slide - 29
Figure 10.9: Type 2 functional responses of (a) damselfly nymphs and (b) bank voles. BIOS 6150: Ecology - Dr. S. Malcolm. Week 6: Predation and predatory behavior Slide - 30
Figure 9.7 (3 rd ed.): Type 2 functional responses in a parasitoid and effect of experience BIOS 6150: Ecology - Dr. S. Malcolm. Week 6: Predation and predatory behavior Slide - 31
Figure 10.8: Type 1 functional response in Daphnia filter-feeding yeast. BIOS 6150: Ecology - Dr. S. Malcolm. Week 6: Predation and predatory behavior Slide - 32
Figure 10.10: Type 3 functional response in: (a) shrews & mice, (b,d) flies, (c,e) wasp parasitoid BIOS 6150: Ecology - Dr. S. Malcolm. Week 6: Predation and predatory behavior Slide - 33
Figure 9.10 (3 rd ed.): Negative impact of mutual interference increases with forager density BIOS 6150: Ecology - Dr. S. Malcolm. Week 6: Predation and predatory behavior Slide - 34
Figure 9.11 (3 rd ed.): Aggregative responses of foragers to host or prey density BIOS 6150: Ecology - Dr. S. Malcolm. Week 6: Predation and predatory behavior Slide - 35
Figure 9.22 (3 rd ed.): Interaction between aggregative and functional responses BIOS 6150: Ecology - Dr. S. Malcolm. Week 6: Predation and predatory behavior Slide - 36
Figure 5.19: Effect of tide fluctuations on the distributions of predatory whelks and their barnacle prey. Begon, Mortimer & Thompson (1996) BIOS 6150: Ecology - Dr. S. Malcolm. Week 6: Predation and predatory behavior Slide - 37
Figure 9.27: Ideal-free distribution in foraging ducks BIOS 6150: Ecology - Dr. S. Malcolm. Week 6: Predation and predatory behavior Slide - 38
Figure 9.22: The marginal value theorem BIOS 6150: Ecology - Dr. S. Malcolm. Week 6: Predation and predatory behavior Slide - 39
Figure 9.23: Predicted and observed foraging times spent by great tits in prey patches with different traveling times. BIOS 6150: Ecology - Dr. S. Malcolm. Week 6: Predation and predatory behavior Slide - 40