Open removal models with temporary emigration and population dynamics to inform invasive animal management

Abstract

Removal sampling data are the primary source of monitoring information for many populations (e.g., invasive species, fisheries). Population dynamics, temporary emigration, and imperfect detection are common sources of variation in monitoring data and are key parameters for informing management. We developed two open robustdesign removal models for simultaneously modeling population dynamics, temporary emigration, and imperfect detection: a random walk linear trend model (estimable without ancillary information), and a 2-age class informed population model (InfoPM, closely related to integrated population models) that incorporated prior information for age-structured vital rates and relative juvenile availability. We applied both models to multiyear, removal trapping time-series of a large invasive lizard (Argentine black and white tegu, Salvator merianae) in three management areas of South Florida to evaluate the effectiveness of management programs. Although estimates of the two models were similar, the InfoPMs generally returned more precise estimates, partitioned dynamics into births, deaths, net migration, and provided a decision support tool to predict population dynamics under different effort scenarios while accounting for uncertainty. Trends in tegu superpopulation abundance estimates were increasing in two management areas despite generally high removal rates. However, tegu abundance appeared to decline in the Core management area, where trapping density was the highest and immigration the lowest. Finally, comparing abundance predictions of no-removal scenarios to those estimated in each management area suggested significant population reductions due to management. These results suggest that local tegu population control via systematic trapping may be feasible with high enough trap density and limited immigration; and highlights the value of these trapping programs. We provided the first estimates of tegu abundance, capture probabilities, and population dynamics, which is critical for effective management. Furthermore, our models are applicable to a wide range of monitoring programs (e.g., carcass recovery or removal point-counts).

Burmese pythons in Florida: A synthesis of biology, impacts, and management tools

“…For example, removal of unmarked animals (without release), is common for management and monitoring of invasive species (e.g., invasive carp, Cupp et al 2021), yet it does not account for variation in detection, rendering interpretation of removal counts challenging (Anderson 2001). Removal models have been developed to estimate abundance based on removals of animals from a population (Moran 1951;Zippen 1956) and have been expanded to incorporate spatially distinct sites that are demographically closed (Dorazio et al 2005(Dorazio et al , 2008Ruiz and Laplanche 2010;Davis et al 2016), sites with open populations (Matechou et al 2016), and robust design (Link et al 2018;Udell et al 2022). Recently, removal models have been extended to better match the management time frames of invasive species control (i.e., years).…”

Evidencing success: Data requirements to model the impacts of long-term management of invasive squirrels

“…Various model formulations exist that target specific challenges but removal models remain complex with ongoing developments (Udell et al, 2022) and challenging data requirements. The estimation procedure will be compromised when operations are undertaken that do not allow detection of a decrease in population abundance.…”

Skin lipids alone enable conspecific tracking in an invasive reptile, the Argentine black and white tegu lizard (Salvator merianae)

“…The species is also a growing management concern in the southeastern United States due to their broad habitat use and high tolerance to cold temperatures, enabling significant potential for range expansion [ 22 ]. Contemporary management tools available to managers, predominantly various configurations of live traps baited with eggs [ 23 ], have been reported as being inadequate, with additional methods/tools being needed to protect natural resources from invasive tegus [ 24 ].…”