title: Topographic determinants of mobile vertebrate predator hotspots: current knowledge and future directions.
abstract: Despite being identified as a driver of mobile predator aggregations (hotspots) in both marine and terrestrial environments, topographic complexity has long remained a challenging concept for scientists to visualise and a difficult parameter to estimate. It is only with the advent of high-speed computers and the recent popularisation of geographical information systems (GIS) that terrain attributes have begun to be quantitatively measured in three-dimensional space and related to wildlife dynamics, making the well-established field of geomorphometry (or 'digital terrain modelling') a discipline of growing appeal to biologists. Although a diverse array of numerical metrics is now available to describe the shape, geometry and physical properties of natural habitats, few of these are known to, or adequately used by, ecologists. In this review, we examine the nature and usage of 56 geomorphometrics extracted from the ecological modelling literature over a period of 32 years (1979-2011). We show that, in studies of mobile predators, numerous topographic variables have largely been overlooked in favour of single basic metrics that do not, on their own, fully capture the complexity of continuous landscapes. Based on a simulation approach, we assess the redundancy and correlation structure of these metrics and demonstrate that a majority are highly collinear. We highlight a suite of 7-8 complementary metrics which best explain topographic patterns across a bathymetric grid of the west Australian seafloor, and contend that field and analytical protocols should prioritise variables of these types, particularly when the responses of predator populations to physical habitat features are of interest. We suggest that prominent structures such as canyons, seamounts or mountain chains can serve as useful proxies for predator hotspots, especially in remote locations where access to high-resolution biological data is often limited.
authors.affiliation: The UWA Oceans Institute, School of Animal Biology, The University of Western Australia, Crawley, Western Australia 6009, Australia.
authors.forename: Phil J
authors.identifier: http://orcid.org/0000-0002-2144-2049
authors.initials: PJ
authors.lastname: Bouchet
authors.affiliation: The UWA Oceans Institute, School of Animal Biology, The University of Western Australia, Crawley, Western Australia 6009, Australia.|Centre for Marine Futures, The University of Western Australia, Crawley, Western Australia 6009, Australia.
authors.forename: Jessica J
authors.initials: JJ
authors.lastname: Meeuwig
authors.affiliation: Centre for Marine Science and Technology, Curtin University, Perth, Western Australia 6845, Australia.
authors.forename: Chandra P
authors.initials: CP
authors.lastname: Salgado Kent
authors.affiliation: Centre for Marine Futures, The University of Western Australia, Crawley, Western Australia 6009, Australia.
authors.forename: Tom B
authors.initials: TB
authors.lastname: Letessier
authors.affiliation: Centre for Whale Research (WA) Inc., Fremantle, Western Australia 6959, Australia.
authors.forename: Curt K
authors.initials: CK
authors.lastname: Jenner
mesh_terms: D000818:Animals; D001315:Australia; D004777:Environment; D005843:Geography; D008954:Models, Biological; D011235:Predatory Behavior; D014714:Vertebrates
keywords: aggregations; complexity; geomorphometry; hotspots; landscape; metrics; predators; topography