DOI: 10.5061/dryad.1m081
title: Data from: Does movement behaviour predict population densities? a test with 25 butterfly species

description: Diffusion, which approximates a correlated random walk, has been used by
 ecologists to describe movement, and forms the basis for many theoretical
 models. However, it is often criticized as too simple a model to describe
 animal movement in real populations. We test a key prediction of diffusion
 models, namely, that animals should be more abundant in land cover classes
 through which they move more slowly. This relationship between density and
 diffusion has rarely been tested across multiple species within a given
 landscape. We estimated diffusion rates and corresponding densities of 25
 Israeli butterfly species from flight path data and visual surveys. The
 data were collected across 19 sites in heterogeneous landscapes with four
 land cover classes: semi-natural habitat, olive groves, wheat fields and
 field margins. As expected from theory, species tended to have higher
 densities in land cover classes through which they moved more slowly and
 lower densities in land cover classes through which they moved more
 quickly. Two components of movement (move length and turning angle) were
 not associated with density, nor was expected net squared displacement.
 Move time, however, was associated with density, and animals spent more
 time per move step in areas with higher density. The broad association we
 document between movement behaviour and density suggests that diffusion is
 a good first approximation of movement in butterflies. Moreover, our
 analyses demonstrate that dispersal is not a species-invariant trait, but
 rather one that depends on landscape context. Thus, land cover classes
 with high diffusion rates are likely to have low densities and be
 effective conduits for movement.
description: Israeli_butterfly_move_dataPrimary data for estimating movement rates. UniqueID combines the site name, track number and flight step number. Species are identified in Supplemental Information, Table S3. Field types are Wheat and Olives. Locations are Wheat, Olive, Nature and (Field) Margin. See Figure 1 for visual of field types vs locations. Projected coordinate system is GRS_1980_Transverse_Mercator with False Easting = 219529.584 and False Northing = 626907.390. Each move consisted of a move length, measured as the distance between turning or stopping points i and i+1, and a turning angle θi , measured as the angle between move i-1 and i. The file contains Time (seconds), Length (m) and Turn (Cosine of turning angle). Note that steps starting in edge regions, defined as 10m outside the Margin towards Nature or Fields, were omitted from the analysis (see text for details). However, if a move step starts in one of the included Locations and ends in edge region, the step and associated angle and time was included in the analysis.Israeli_butterfly_diffusion rates_and _densitiesParameters calculated via bootstrapping of movement data and densities (number/ha) from surveys across the sites (see text for details). Parameters include diffusion (m2/sec), Turn (cos of turning angle), Length (move step, m). Time (sec) and Er2 (expected net squared displacement, m2). File includes median and 95% confidence intervals for each parameter. Locations are Wheat, Olive, Nature and (Field) Margin. Wingspan is in cm.