Main Points. Terms: functional response, prey switching, apparent competition, ecosystem management

Transcription

1 Main Points 1) Functional responses of predators -- prey switching and prey preferences -- Example: removing protected populations to save an endangered species -- apparent competition and the decline of species of conservation concern -- Example: apparent competition between caribou and moose 2) Ecosystem (or multi-species) approaches to conservation -- Example: using cattle to offset apparent competition and conserve a declining antelope Pre-reading: Tuesday 9 Oct = Beston et al Thursday 11 Oct = NA Terms: functional response, prey switching, apparent competition, ecosystem management First set of presentations on single species and multi-species conservation Thursday 11 October. If you are not presenting, print off different group evaluations from the website and bring to class. These are for your own notes, to be typed up and turned in 16 October. 1

2 Quality = Style + Content Style (45pts): 1) did all group members participate more or less equally in the presentation, and in answering questions? 2) was the delivery clear and professional? In other words, was jargon minimized, were terms well defined, was the delivery polished, and was the material wellunderstood by the presenters? 3) did all group members seem equally familiar with all of the material presented? In other words, were transitions between partners seamless, or did transitions seem awkward, like 3 mini-presentations? 4) did speakers look at the audiences (as opposed to notes)? 5) were scientific studies cited when they were referenced? 6) did speakers end statements with question marks? 7) were there lots of fallback words used (uh, um, like, sort of, etc)? Content (45pts): 1) was the presentation focused with a logical introduction, statement of controversy, references to the scientific literature (as opposed to the internet or magazine articles)? 2) were examples used to illustrate concepts, or was the presentation just a series of examples? 3) were facts (data) from scientific studies used instead of claims and anecdotes? 4) were figures and tables explained clearly and succinctly? 5) were slides free of spelling errors and other mistakes? Was use of text on slides minimal? 6) were speakers able to answer questions posed by the audience? 7) did speakers ask the other group thoughtful questions? 2

3 Functional Responses Functional Response: the response of a predator to the abundance of prey. 3

4 Functional Responses Functional Response: the response of a predator to the abundance of prey. Involves the question Does the number of prey an individual predator eats depend on that prey s abundance? Deals with changes in predator behavior (not predator numbers). 4

5 Functional Responses Functional Response: the response of a predator to the abundance of prey. # prey consumed by predator prey abundance Type 1 Functional Response the number of prey consumed increases without limit with increasing prey abundance. 5

6 Functional Responses Functional Response: the response of a predator to the abundance of prey. # prey consumed by predator prey abundance Type 2 Functional Response The number of prey consumed rises steeply at first, then levels off. 6

7 Functional Responses Prey switching: predators switch between different species of prey when alternative sources of prey are abundant, reducing pressure on the prey population. # prey consumed by predator prey abundance Type 3 Functional Response The number of prey consumed increases with increasing prey abundance, then levels off as prey switching occurs. 7

8 Discussion Q: what would cause a predator to exhibit behavior consistent with a Type 2 versus Type 3 functional response? # prey consumed by predator prey abundance 8

9 Functional Responses of Predators and Allee effects of Prey 9

10 Functional Responses of Predators and Allee effects of Prey Courchamp et al Science. 10

11 Prey Switching and Prey Preferences Wittmer et al Oecologia. 11

12 Prey Switching and Prey Preferences caribou show evidence of an Allee effect, implying that food isn t limiting. Wittmer et al Oecologia. 12

13 Prey Switching and Prey Preferences? 13

14 Prey Switching and Prey Preferences _ 14

15 Discussion Q: Why does the dashed arrow only point to the caribou? In other words, why don t moose experience more predation because of caribou? _ 15

16 Prey Switching and Prey Preferences Apparent competition: indirect negative interaction incurred by one (or more) prey species because of a shared predator. _ 16

17 Prey Switching and Prey Preferences Serrouya et al Peer J. 17

18 Prey Switching and Prey Preferences Apparent competition has been implicated in the declines of many species of conservation concern. Typically involves either introduction of a novel primary prey (that subsidizes predators), habitat alteration, or both. 18

19 Conservation Beyond Species ,

20 Conservation Beyond Species of the 1.7 million species described on Earth, an estimated 40% are threatened with extinction (IUCN 2006). most of these are little known, uncharismatic, economically unimportant species that are not foundation, keystone, or umbrella species. 20

21 Conservation Beyond Species ecosystem (or multi-species) management = an approach to maintaining or restoring the composition, structure, and function of ecosystems for long-term sustainability. 21

22 Umbrella Species as a Happy Medium? Rowland et al Biol. Cons. 28

23 Umbrella Species as a Happy Medium? Umbrella species should: -- be relatively widespread -- have resource requirements that overlap with other species of conservation concern -- be neither rare nor cosmopolitan 23

24 Conservation Beyond Species ecosystem (or multi-species) management = an approach to maintaining or restoring the composition, structure, and function of ecosystems for long-term sustainability. Differs from a species-specific approach in combining ecological, socioeconomic, and institutional perspectives. Typically characterized by proactivity (as opposed to reactivity)

25 Predators, Livestock Production, and Apparent Competition Laikipia District consists of ~10,000 km 2 managed jointly for cattle production and tourism no formal protection; entirely voluntary highest abundances of wildlife anywhere in Kenya 25

26 Predators, Livestock Production, and Apparent Competition Observation 1: plains zebra and cattle have not declined over a 20-year time period; their numbers are controlled by rainfall From Georgiadis et al

27 Predators, Livestock Production, and Apparent Competition Observation 2: some antelopes have declined concurrently with a shift in ranchers attitudes towards predators hartebeest waterbuck common eland buffalo From Georgiadis et al

28 Predators, Livestock Production, and Apparent Competition Observation 3: zebra prefer to graze in areas where cattle recently have been corralled day 2 day 1 day 28 day

29 Lions selectively kill hartebeest

30 Experimental removal of lions

31 0 0 Sa F a Sc Ssa Sa 2 treatments (lions, no lions) x 3 years ( ) Sa Sc Ssa Fa

32 Lions suppress hartebeest populations λ = λ =

33 Lions drive an Allee effect Hartebeest exhibit inverse density-dependence in the presence of lions, and negative density-dependence where lions have been experimentally removed.

34 How have hartebeest coexisted with lions for thousands of years? Historical baseline Pre-1950s Lethal control of lions 1950s-mid 1980s Restoration of lions 1980s-present

35 How have hartebeest coexisted with lions for thousands of years? Historical baseline Pre-1950s Lethal control of lions + Fire suppression 1950s-mid 1980s Restoration of lions + Fire suppression + Tree encroachment mid 1980s-present?

36 Lion and hartebeest numbers are correlated negatively

37 +

38 Functional responses and spatial refuges

39 Functional responses and spatial refuges

40 Glade creation experiment In 2010, constructed bomas standardized for the following: cattle m diameter -- active for 1 month

41 Glade creation experiment After 3 years, zebra were attracted to glades (β = 1.02 ± 0.69 CI) After 3 years, hartebeest avoided glades (β = ± 0.95 CI) zebra + experimental glades hartebeest + experimental glades

42 Predators, Livestock Production, and Apparent Competition 42

43 Glades tripled mortality due to lion predation for hartebeest No glade in territory Glade in territory Constructed frailty models for hartebeest survival Odds = 2.969, S.E. = 0.232, P < 0.001