Effects of body size on estimation of mammalian area requirements.
Noonan MJ., Fleming CH., Tucker MA., Kays R., Harrison A-L., Crofoot MC., Abrahms B., Alberts SC., Ali AH., Altmann J., Antunes PC., Attias N., Belant JL., Beyer DE., Bidner LR., Blaum N., Boone RB., Caillaud D., de Paula RC., de la Torre JA., Dekker J., DePerno CS., Farhadinia M., Fennessy J., Fichtel C., Fischer C., Ford A., Goheen JR., Havmøller RW., Hirsch BT., Hurtado C., Isbell LA., Janssen R., Jeltsch F., Kaczensky P., Kaneko Y., Kappeler P., Katna A., Kauffman M., Koch F., Kulkarni A., LaPoint S., Leimgruber P., Macdonald DW., Markham AC., McMahon L., Mertes K., Moorman CE., Morato RG., Moßbrucker AM., Mourão G., O'Connor D., Oliveira-Santos LGR., Pastorini J., Patterson BD., Rachlow J., Ranglack DH., Reid N., Scantlebury DM., Scott DM., Selva N., Sergiel A., Songer M., Songsasen N., Stabach JA., Stacy-Dawes J., Swingen MB., Thompson JJ., Ullmann W., Vanak AT., Thaker M., Wilson JW., Yamazaki K., Yarnell RW., Zieba F., Zwijacz-Kozica T., Fagan WF., Mueller T., Calabrese JM.
Accurately quantifying species' area requirements is a prerequisite for effective area-based conservation. This typically involves collecting tracking data on species of interest and then conducting home-range analyses. Problematically, autocorrelation in tracking data can result in space needs being severely underestimated. Based on previous work, we hypothesized the magnitude of underestimation varies with body mass, a relationship that could have serious conservation implications. To evaluate this hypothesis for terrestrial mammals, we estimated home-range areas with GPS locations from 757 individuals across 61 globally distributed mammalian species with body masses ranging from 0.4 to 4,000 kg. We then applied block cross-validation to quantify bias in empirical home-range estimates. Area requirements of mammals <10 kg were underestimated by a mean ∼15%, and species weighing ∼100 kg were underestimated by ∼50% on average. Thus, we found area estimation was subject to autocorrelation-induced bias that was worse for large species. Combined with the fact that extinction risk increases as body mass increases, the allometric scaling of bias we observed suggests the most threatened species are also likely to be those with the least accurate home-range estimates. As a correction, we tested whether data thinning or autocorrelation-informed home-range estimation minimized the scaling effect of autocorrelation on area estimates. Data thinning required ankk ∼93% data loss to achieve statistical independence with 95% confidence and was therefore not a viable solution. In contrast, autocorrelation-informed home-range estimation resulted in consistently accurate estimates irrespective of mass. When relating body mass to home range size, we detected that correcting for autocorrelation resulted in a scaling exponent significantly >1, meaning the scaling of the relationship changed substantially at the upper end of the mass spectrum. Article impact statement: Due to autocorrelation-induced bias, conventional methods severely underestimate the area requirements of GPS-tracked large mammals. Efectos del Tamaño Corporal sobre la Estimación de los Requerimientos de Área de Mamíferos This article is protected by copyright. All rights reserved.