Skip to content

Research at St Andrews

Estimating abundance of cryptic but trappable animals using trapping point transects: a case study for Key Largo woodrats

Research output: Research - peer-reviewArticle



1. Obtaining robust abundance or density estimates is problematic for many rare or cryptic species. We combine elements of capture-recapture and distance sampling, to develop a method called trapping point transects (TPT).
2. TPT requires two separate surveys to be held concurrently in space and time. In the main survey, the encounter rate (number of animals caught per trap per session) is measured. In the trial survey, animals whose locations are known prior to opening traps are used to estimate the detection function g(r) (the probability of capturing an animal given it is distance r from a trap when it is set), so the effective trapping area in the main survey can be estimated. It is assumed animals in the trial survey are a representative sample of all animals in the population. Individual heterogeneity in trappability is accommodated using random effects in g(r).
3. Performance of two TPT estimators was assessed by simulation. Generally, when underlying capture probabilities were high (g(0)=0.8) and between-individual variation was small, modest survey effort (360 trap nights in the trial survey) generated little bias in estimated abundance (c. 5%). Uncertainty and relative bias in population estimates increased with decreasing capture probabilities and increasing between-individual variation. Survey effort required to obtain unbiased estimates was also investigated.
4. Abundance of the endangered Key Largo woodrat (Neotoma floridana smalli) was estimated using TPT between 2008-2011, yielding annual estimates of the extant wild population of 693, 248, 78, and 256 animals, with CVs of 0.45, 0.55, 0.82 and 0.43, respectively.
5. TPT was found to be a cost-efficient monitoring method, and could be adapted to a range of species that are otherwise very difficult to monitor. For example, detection of animals at the sample point might rely on camera traps, or different lures (e.g., vocal-playback or baits). We anticipate that TPT surveys will see wide usage for estimating population abundance of cryptic but trappable species.


Original languageEnglish
Pages (from-to)695-703
JournalMethods in Ecology and Evolution
StatePublished - 2012

Discover related content
Find related publications, people, projects and more using interactive charts.

View graph of relations

Related by author

  1. Model-based approaches to deal with detectability: a comment on Hutto (2016a)

    Marques, T. A., Thomas, L., Kery, M., Buckland, S. T., Borchers, D. L., Rexstad, E., Fewster, R. M., Mackenzie, D. I., Royle, J. A., Guillera-Arroita, G., Handel, C. M., Pavlacky, D. C. & Camp, R. J. Jul 2017 In : Ecological Applications. 27, 5, p. 1694-1698 5 p.

    Research output: Research - peer-reviewLetter

  2. Estimating Key Largo woodrat abundance using spatially explicit capture–recapture and trapping point transects

    Potts, J. M., Buckland, S. T., Thomas, L. & Savage, A. Jun 2016 In : Wildlife Society Bulletin. 40, 2, p. 331-338

    Research output: Research - peer-reviewArticle

  3. The effect of animal movement on line transect estimates of abundance

    Glennie, R., Buckland, S. T. & Thomas, L. 23 Mar 2015 In : PLoS One. 10, 3, e0121333

    Research output: Research - peer-reviewArticle

  4. Statistical ecology comes of age

    Gimenez, O. , Buckland, S. T. , Morgan, B. J. T. , Bez, N. , Bertrand, S. , Choquet, R. , Dray, S. , Etienne, M-P. , Fewster, R. , Gosselin, F. , Merigot, B. , Monestiez, P. , Morales, J. M. , Mortier, F. , Munoz, F. , Ovaskainen, O. , Pavoine, S. , Pradel, R. , Schurr, F. M. , Thomas, L. & 4 others Thuiller, W., Trenkel, V., de Valpine, P. & Rexstad, E. 24 Dec 2014 In : Biology Letters. 10, 4 p., 20140698

    Research output: Research - peer-reviewArticle

  5. Distance Sampling

    Marques, T. A., Buckland, S. T., Borchers, D. L., Rexstad, E. & Thomas, L. 1 Dec 2014 International Encyclopedia of Statistical Science. Lovric, M. (ed.). Springer, p. 398 400 p.

    Research output: ResearchChapter

Related by journal

  1. Attributing changes in the distribution of species abundance to weather variables using the example of British breeding birds

    Oedekoven, C. S., Elston, D. A., Harrison, P. J., Brewer, M. J., Buckland, S. T., Johnston, A., Foster, S. & Pearce-Higgins, J. W. Dec 2017 In : Methods in Ecology and Evolution. 8, 12, p. 1690-1702

    Research output: Research - peer-reviewArticle

  2. Distance sampling with camera traps

    Howe, E. J., Buckland, S. T., Després-Einspenner, M-L. & Kühl, H. Nov 2017 In : Methods in Ecology and Evolution. 8, 11, p. 1558-1565

    Research output: Research - peer-reviewArticle

  3. Inference of selection gradients using performance measures as fitness proxies

    Franklin, O. D. & Morrissey, M. B. Jun 2017 In : Methods in Ecology and Evolution. 8, 6, p. 663-677 15 p.

    Research output: Research - peer-reviewArticle

  4. Echolocation detections and digital video surveys provide reliable estimates of the relative density of harbour porpoises

    Williamson, L. D., Brookes, K. L., Scott, B. E., Graham, I. M., Bradbury, G., Hammond, P. S. & Thompson, P. M. 13 Jul 2016 In : Methods in Ecology and Evolution. 7, 7, p. 762-769 8 p.

    Research output: Research - peer-reviewArticle

Related by journal

  1. Methods in Ecology and Evolution (Journal)

    Gaggiotti, O. E. (Member of editorial board)
    1 Sep 2014 → …

    Activity: Publication peer-review and editorial workEditor of research journal

ID: 19526765