title: Estimating home-range size: when to include a third dimension?
abstract: Most studies dealing with home ranges consider the study areas as if they were totally flat, working only in two dimensions, when in reality they are irregular surfaces displayed in three dimensions. By disregarding the third dimension (i.e., topography), the size of home ranges underestimates the surface actually occupied by the animal, potentially leading to misinterpretations of the animals' ecological needs. We explored the influence of considering the third dimension in the estimation of home-range size by modeling the variation between the planimetric and topographic estimates at several spatial scales. Our results revealed that planimetric approaches underestimate home-range size estimations, which range from nearly zero up to 22%. The difference between planimetric and topographic estimates of home-ranges sizes produced highly robust models using the average slope as the sole independent factor. Moreover, our models suggest that planimetric estimates in areas with an average slope of 16.3° (±0.4) or more will incur in errors ≥5%. Alternatively, the altitudinal range can be used as an indicator of the need to include topography in home-range estimates. Our results confirmed that home-range estimates could be significantly biased when topography is disregarded. We suggest that study areas where home-range studies will be performed should firstly be scoped for its altitudinal range, which can serve as an indicator for the need for posterior use of average slope values to model the surface area used and/or available for the studied animals.
authors.affiliation: CIBIO Centro de Investigação em Biodiversidade e Recursos Genéticos, Universidade do Porto, Inbio - Laboratório Associado, Campus Agrário de Vairão 4485 - 661, Vairão, Portugal ; Departamento de Biologia, Faculdade de Ciências, Universidade do Porto Rua do Campo Alegre s/n, 4150-150, Porto, Portugal ; Instituto de Investigación en Recursos Cinegéticos (IREC CSIC-UCLM-JCCM) Ronda de Toledo s/n, 13005, Ciudad Real, Spain.
authors.forename: Pedro
authors.initials: P
authors.lastname: Monterroso
authors.forename: Neftalí
authors.initials: N
authors.lastname: Sillero
authors.forename: Luís Miguel
authors.initials: LM
authors.lastname: Rosalino
authors.forename: Filipa
authors.initials: F
authors.lastname: Loureiro
authors.forename: Paulo Célio
authors.initials: PC
authors.lastname: Alves
keywords: Mammalian ecology; modeling; planimetric home-range; slope threshold; topographic home-range
references.citation: Folia Primatol (Basel). 2009;80(2):89-103
references.pmid: 19546574
references.citation: Am J Primatol. 2000 Nov;52(3):143-7
references.pmid: 11078028
references.citation: Oecologia. 1992 Aug;91(1):75-81
references.pmid: 28313377
references.citation: Am J Primatol. 2008 Sep;70(9):871-8
references.pmid: 18548511
references.citation: J Theor Biol. 1978 Dec 7;75(3):327-37
references.pmid: 745446