Download presentation

Presentation is loading. Please wait.

Published byAinsley Akey Modified over 2 years ago

1
Island eradications: Approaches and assessment of success Biodiversity Bonanza Dean Anderson Landcare Research

2
Central question: How can we determine whether an eradication effort has been successful?

3
Answer is important: 1)Influence management practice 2)Funders want to know outcome 3)If fail, want to know sooner rather than later.

4
Assessing success Establish relationship between search effort and probability of detection. Actively search for survivors Collect spatial and temporal data on search effort

5
Key relationship 1 0 Search effort Probability of detection

6
Probability of detection and success 1 0 Search effort Probability of detection Probability of eradication success

7
Probability of detection and success 1 0 Search effort Probability of detection Probability of eradication success Threshold

8
Probability of detection and success 1 0 Search effort Probability of detection Probability of eradication success

9
How do we get this “key” relationship? 1 0 Search effort Probability of detection Depends on eradication method

10
Carcasses collected Pigs on Santa Cruz Island, USA - (Ramsey et al. 2009) Stoats on Resolution Island, NZ DOC Goats on Guadalupe Island, Mexico -Luciana Luna, Conservacion de Islas

11
Catch – effort model: (knock-down phase) Helicopter Ground Goats dispatched Hunting hours

12
Probability of detection and success 1 0 Search effort Probability of detection Probability of eradication success

13
No carcasses: Rat Eradication with single toxin drop

14
2 Approaches when missing carcasses 1)Wait and see –Easy –Takes time –If fail, the problem is big 2)Actively search –Requires data and statistics –If fail, survivors may be very localised

15
Isabel 82 ha Mexico Pacific Ocean Gulf of Mexico Araceli Samaniego Conservacion de Islas

16
Isabel Island, Mexico 1 toxin drop 3 annual wax-tag surveys No rats detected

17
Eradication success??? Spatial-detection Model Home range size Detection probability of tags

18
Wax-tag survey year 2 Spatial-detection Model Home range size Detection probability of tags Population growth rate Dispersal kernel

19
Wax-tag survey year 3

20
Repeat 1000 times Each female takes on slightly different parameter values

21
Results MedianLow 2.5% CIHigh 97.5 CI Prob. Success 2009 0.740.620.83 Prob. Success 2010 0.960.760.99 Prob. Success 2011 0.99 1.00 * Confidence intervals reflect the uncertainty in input parameters

22
Results MedianLow 2.5% CIHigh 97.5 CI Prob. Success 2009 0.740.620.83 Prob. Success 2010 0.960.760.99 Prob. Success 2011 0.99 1.00 * Confidence intervals reflect the uncertainty in input parameters

23
One – survey approach

24
50-m spacing

25
Summary Why quantify probability of success? –Management –Funders –Identify failure early

26
Summary Carcasses counted 1)Catch – effort model Collect data during “knock-down” phase Establish relationship between detection & effort

27
Summary Carcasses not available 2)Spatial – detection model Estimate parameters with experiments or literature –Homerange size –Detection probability of device –Reproductive rates –Dispersal kernels Incorporate uncertainty

28
Summary Requires biological understanding and statistics Arguably better than “wait-and-see”

29
Acknowledgements John Parkes Araceli Samaniego Luciana Luna Conservacion de Islas, Mexico Department of Conservation, NZ

Similar presentations

© 2017 SlidePlayer.com Inc.

All rights reserved.

Ads by Google