Title: FORAGING ECOLOGY, VIGILANCE OF COYOTES,
1FORAGING ECOLOGY, VIGILANCE OF COYOTES, AND
BEHAVIORAL CASCADES IN RESPONSE TO GRAY WOLF
REINTRODUCTION IN YELLOWSTONE NATIONAL PARK
T. Adam Switalski Post-Project Seminar December
11, 2001
2Introduction
- Species loss
- Carnivores particularly at risk
- Inherent rarity
- Large habitat requirements
- Competition with humans
3Introduction
- Extirpation of Keystone Predators leads to
- Disturbed unstable systems
- Increased numbers of prey and competing
carnivores - Expanded range
- Loss of anti-predatory behaviors
- Vigilance
- Avoidance
- Ultimately, cascading effects
4Wolf Range Past, Present, and Future
5Introduction
- Case study reintroduction of wolves in
Yellowstone National Park - How are coyotes learning to coexist with wolves?
- How are other species responding numerically and
behaviorally? - What are the cascading effects?
6Foraging Ecology and Vigilance of Coyotes in
Response to Wolf Reintroduction
- Introduction
- Study area
- Methods
- Results
- Discussion
7Coyote and Wolf Coexistence
- No coexistence
- Resource partitioning
- Spatial avoidance
- Temporal separation
- Low degree of diet overlap
- Different habitat use
8Return of the Wolf to YNP
- Historical coexistence
- 1995, wolves translocated from Canada
- Designated nonessential experimental population
- Population increased quickly with highest
fecundity recorded for species
9Foraging Ecology and Vigilance Research Questions
10Foraging Ecology and Vigilance Research Questions
- Do coyotes exhibit different behavioral time
budgets now as compared to before wolves were
reintroduced into YNP?
11Foraging Ecology and VigilanceResearch Questions
- Do coyotes exhibit different behavioral time
budgets now as compared to before wolves were
reintroduced into YNP? - Do coyotes living between wolf packs (buffer
zones) exhibit different behavioral time budgets
than coyotes in high wolf use areas?
12Foraging Ecology and Vigilance Research Questions
- Now that wolves have become established in the
Lamar Valley, do coyotes exhibit different
behavioral time budgets when wolves are
physically present as opposed to their absence?
13Study Area Lamar Valley
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16Food Resources
17Methods
- Observations of coyotes and wolves from
winter 1998 to summer 2000
18Methods
- Recorded
- Wolf and coyote location
- Type of behavior and time of day
- Travel route
- Location of behavior
- Sex
- Social status
- Age class
- Pack
- Pack size
19Coyote Behaviors
- Rest (alert, sleep)
- Travel
- Hunting small mammals
- Feeding on carcass
- Vigilance
- Howling
- Other
20 Small Mammal Surveys
- Captured during summer 1999 and 2000
- 3 different sites for 2 sessions each year
- Mini-grids trapped for 4 days 5 nights and
checked twice daily - Once identified, the small mammals were
- Toenail clipped
- Weighed
- Sexed
- Released
21 Statistics
- SAS
- Factorial (split-plot) design
- Analysis of variance using PROC MIXED
- Snow depth was repeated measure
- Sample unit was the individual coyote
- Proportion of time
- Each observation was given equal weight
22 Statistics
- Variables analyzed included
- Wolf activity
- Wolf presence
- Sex
- Year
23 Results
- From December 1997 to July 2000 we made
- 1243 observations of coyotes
- 1743 h of coyote activity budgets
- 28 resident coyotes from 9 packs
- 16 male and 12 females
- 24 alphas and 4 betas
24Lamar Valley Coyotes
- For 60 years, coyotes thrived without wolves
- Coyote population reduced 25 to 33 each winter
- 23 observed coyote mortalities
- Average pack size 3.2 (range 2.7-3.7)
- Very low recruitment (predation and parvo)
25Lamar Valley Wolves
- Druid Peak and Rose Creek packs introduced into
Lamar Valley in 1995 and 1996 - Pack sizes
- 7-8 adults in Druid Peak
- 15-22 adults in Rose Creek
- Druid Peak pack denned within study area
- Wolf territories overlapped creating buffer
zone
26Coyote and Wolf Pack Territories Including Wolf
Buffer Zone
27Mean Snow Depth
28Coyote Behavioral Time Budgets Before and After
Reintroduction
29Coyote Behavioral Time Budgets
30Coyote Behavioral Time Budgets
31Coyote Behavioral Time Budgets
32Coyote Behavioral Time Budgets
33Coyote Behavioral Time Budgets
34Coyote Behavioral Time Budgets
35Different Levels of Wolf Activity
36Presence and Absence of Wolves
37Discussion
- In response to wolf reintroduction coyotes have
adjusted their behavior - Spatially (buffer zone vs. non-buffer zone)
- Temporally (present vs. absent)
38How has coyote behavior changed?
- Increase in the amount of time feeding on
carcasses - Consistent with wolf recolonization in NW Montana
(Arjo and Pletscher 1999) - Feeding on carcasses throughout the year
- Contrasts Gese et al. (1996)
- Decrease in travel
39Energetic Benefits
- Wild coyotes need 930 g of food daily (Bekoff and
Wells 1986) - Coyote must consume the equivalent of
- 27 mice
- 11 microtines
- 6 pocket gophers
- 4 ground squirrels
- or
- Risking a few minutes feeding on a wolf-killed
carcass
40How is behavior different in the buffer zone?
- Wolf buffer zones
- Higher deer survivorship
- Refuge for coyotes
- In YNP, coyotes between Rose Creek and Druid Peak
wolf packs have - Fewer agonistic interactions
- Lower mortality rates
- Different behaviors
41How is behavior different in the buffer zone?
- Coyote behavior in the buffer zone
- Fed on carcasses less
- Little wolf-killed carrion available
- Rested more
- Vigilant less
- Less wary of predation by wolves
42Is Behavior Different Wolf Presence?
- When wolves were present
- Fed on carcasses more
- Wolf-killed carrion almost always present
- Rested less
- Vigilant more
- More wary of predation by wolves
- Most coyotes were killed while scavenging wolf
kills
43Coyote Behavior - Conclusion
- Coyote population reduced
- Surviving coyotes adjusted behavior
- Coyotes benefit from wolf-killed carcasses
- Increased feeding on carcasses
- Increased costs
- Increased vigilance
- Decreased rest
- Higher predation risk
- Impact varies spatially and temporally
44What is the big picture?
- Reintroduction of large carnivores leads to
- Numeric response
- Behavioral response
- Cascading effects
45Numeric Response to Reintroductions
46Numeric Response to Reintroductions
- Contrary results in prey species
- In NW MT, elk and deer populations decreased
- No prey reduction in YNP, MN, and WI
- Reduction of competing carnivores
- Coyote population reduced in NW MT and YNP
47Behavioral Response to Reintroduction
- Minimize encounters
- Adjust spatial and/or temporal use
- Elk in National Elk Refuge dispersed
- Coyotes in NW MT avoided wolves
- Decrease success of attacking predator
- Increased vigilance
48Vigilance
- Aids in
- Detection of predators
- Observation of conspecifics
- Food acquisition
- Prevention of kleptoparasitism
49Environmental and Social Variables
- Group size
- Distance to refuge
- Position in the herd
- Body size
- Age
- Parenthood
- Habitat type
- Predation pressure
- Ecotourism
50Vigilance Conclusions
- Increased risk of predation results in increase
in vigilance - Increase in vigilance increases the animals
safety, however decreases foraging - In GYE since wolf reintroduction
- Elk, moose, and coyotes have increased their
vigilance
51Cascading Effects
- In YNP, reduction of elk population
- Allow vegetation to recover
- Increase population of competing herbivores
- On Isle Royale, increase in wolf population
resulted in - Decrease of moose population
- Recovery of balsam fir
52Behavioral Cascades
- IN YNP, No reduction of elk population, however
behavior changes - Avoiding high wolf use areas
- Aspen and willow recovery
- Higher diversity of song birds
- Increased number of spotted frogs
- Recolonization of beaver
53Behavioral Cascades
- In YNP, decrease in coyote population and
behavior changes - Increase of feeding on carcasses
- Avoidance of high wolf use areas
- Increase in small mammal density
- Increase in the number of badgers, weasels, and
foxes
54Behavioral Cascades the Numeric and Behavioral
Dichotomy
- Behavior changes may reduce fitness
- Increased vigilance in elk may result in
- Reduced fat content and lower body mass in
females - Lower survival rates during the winter
- Calves born with lower weights
- Increased vigilance in coyotes may result in
- Reduced survival of pups
55Conclusion
- Reintroduction of wolves has lead to
- Reduction of prey populations???
- Reduction of competing carnivore population
- Change in behavior
- Increase in anti-predatory behaviors (vigilance)
- Change in space use
- Ultimately, cascading effects may lead to an
increase in biodiversity
56Acknowledgements
- Major Advisor John Bissonette
- Eric Gese, Jim MacMahon, and Bill Adair
- Susan Durham for statistical consultation
- Yellowstone Ecosystem Research Center
- Friends and family