Andy Royle, Ph.D.
Andy Royle has been with Patuxent Wildlife Research Center since 2004. Before that he was a statistician (1998-2004) for the U.S. FWS in the Migratory Bird Management Office where he worked primarily on waterfowl surveys and monitoring projects. Prior to that he was a visiting scientist in the Geophysical Statistics Project at the National Center for Atmospheric Reserach, Boulder, CO. He has a PhD in Statistics (1996) from North Carolina State University and a BS in Fisheries and Wildlife (1990) from Michigan State University.
Science and Products
The Challenge: Research goals of this project are to develop models, statistical methods, sampling strategies and tools for inference about animal population status from survey data. Survey data are always subject to a number of observation processes that induce bias and error. In particular, inferences are based on spatial sampling – we can only ever sample a subset of locations where species...
The Challenge: For decades, capture-recapture methods have been the cornerstone of ecological statistics as applied to population biology. While capture-recapture has become the standard sampling and analytical framework for the study of population processes (Williams, Nichols & Conroy 2002) it has advanced independent of and remained unconnected to the spatial structure of the population...
Occupancy in community-level studies
Another type of multi-species studies, are those focused on community-level metrics such as species richness. In this chapter we detail how some of the single-species occupancy models described in earlier chapters have been applied, or extended, for use in such studies, while accounting for imperfect detection. We highlight how Bayesian methods...MacKenzie, Darryl I.; Nichols, James; Royle, Andy; Pollock, Kenneth H.; Bailey, Larissa L.; Hines, James
Spatial capture–recapture with partial identity: An application to camera traps
Camera trapping surveys frequently capture individuals whose identity is only known from a single flank. The most widely used methods for incorporating these partial identity individuals into density analyses discard some of the partial identity capture histories, reducing precision, and, while not previously recognized, introducing bias. Here, we...Augustine, Ben C.; Royle, J. Andrew; Kelly, Marcella J.; Satter, Christopher B.; Alonso, Robert S.; Boydston, Erin E.; Crooks, Kevin R.
Concepts and practices: Estimating abundance of prey species using hierarchical model-based approaches
Tigers predominantly prey on large ungulate species, such as sambar (Cervus unicolor), red deer (Cervus elaphus), gaur (Bos gaurus), banteng (Bos javanicus), chital (Axis axis), muntjac (Muntiacus muntjak), wild pig (Sus scrofa), and bearded pig (Sus barbatus). The density of a tiger population is strongly correlated with the density of such prey...Dorazio, Robert; Kumar, N. Samba; Royle, Andy; Gopalaswamy, Arjun M.
Living on the edge: Opportunities for Amur tiger recovery in China
Sporadic sightings of the endangered Amur tiger Panthera tigris altaica along the China-Russia border during the late 1990s sparked efforts to expand this subspecies distribution and abundance by restoring potentially suitable habitats in the Changbai Mountains. To guide science-based recovery efforts and provide a baseline for future monitoring...Wang, Tianming; Royle, Andy; Smith, J.L.D.; Zou, Liang; Lu, Xinyue; Li, Tong; Yang, Haitao; Li, Zhilin; Feng, Rongna; Bian, Yajing; Feng, Limin; Ge, Jianping
Spatially explicit dynamic N-mixture models
Knowledge of demographic parameters such as survival, reproduction, emigration, and immigration is essential to understand metapopulation dynamics. Traditionally the estimation of these demographic parameters requires intensive data from marked animals. The development of dynamic N-mixture models makes it possible to estimate demographic...Zhao, Qing; Royle, Andy; Boomer, G. Scott
Examining the occupancy–density relationship for a low-density carnivore
The challenges associated with monitoring low-density carnivores across large landscapes have limited the ability to implement and evaluate conservation and management strategies for such species. Non-invasive sampling techniques and advanced statistical approaches have alleviated some of these challenges and can even allow for spatially...Linden, Daniel W.; Fuller, Angela K.; Royle, J. Andrew; Hare, Matthew P.
Concepts: Assessing tiger population dynamics using capture–recapture sampling
Capture-recapture can be viewed as an animal survey method in which the count statistic is the total number of animals caught, and the associated detection probability is the probability of capture.Royle, J. Andrew; Gopalaswamy, Arjun M.; Dorazio, Robert; Nichols, James D.; Jathanna, Devcharan; Parameshwaran, Ravishankar
Dynamic optimization of landscape connectivity embedding spatial-capture-recapture information
Maintaining landscape connectivity is increasingly important in wildlife conservation, especially for species experiencing the effects of habitat loss and fragmentation. We propose a novel approach to dynamically optimize landscape connectivity. Our approach is based on a mixed integer program formulation, embedding a spatial capture-recapture...Xue, Yexiang; Wu, Xiaojian; Morin, Dana J.; Dilkina, Bistra; Fuller, Angela K.; Royle, J. Andrew; Gomes, Carla P.
Accounting for imperfect detection of groups and individuals when estimating abundance
If animals are independently detected during surveys, many methods exist for estimating animal abundance despite detection probabilities <1. Common estimators include double-observer models, distance sampling models and combined double-observer and distance sampling models (known as mark-recapture-distance-sampling models; MRDS). When animals...Clement, Matthew J.; Converse, Sarah J.; Royle, J. Andrew
Use of spatial capture–recapture to estimate density of Andean bears in northern Ecuador
The Andean bear (Tremarctos ornatus) is the only extant species of bear in South America and is considered threatened across its range and endangered in Ecuador. Habitat loss and fragmentation is considered a critical threat to the species, and there is a lack of knowledge regarding its distribution and abundance. The species is thought to occur...Molina, Santiago; Fuller, Angela K.; Morin, Dana J.; Royle, J. Andrew
Model-based approaches to deal with detectability: a comment on Hutto (2016)
In a recent paper, Hutto (2016a) challenges the need to account for detectability when interpreting data from point counts. A number of issues with model-based approaches to deal with detectability are presented, and an alternative suggested: surveying an area around each point over which detectability is assumed certain. The article contains a...Marques, Tiago A.; Thomas, Len; Kéry, Marc; Buckland, Steve T.; Borchers, David L.; Rexstad, Eric; Fewster, Rachel M.; MacKenzie, Darryl I.; Royle, Andy; Guillera-Arroita, Gurutzeta; Handel, Colleen M.; Pavlacky, David C. ; Camp, Richard J.
A multistate dynamic site occupancy model for spatially aggregated sessile communities
Estimation of transition probabilities of sessile communities seems easy in principle but may still be difficult in practice because resampling error (i.e. a failure to resample exactly the same location at fixed points) may cause significant estimation bias. Previous studies have developed novel analytical methods to correct for this estimation...Fukaya, Keiichi; Royle, J. Andrew; Okuda, Takehiro; Nakaoka, Masahiro; Noda, Takashi