DOI: 10.5061/dryad.nzs7h44p8
title: Mate searching context of prey influences predator-prey space race

description: Predation risk is a strong driver of prey distribution and movement.
 However, fitness-influencing behaviours, such as mating, can alter risk
 and influence predator-prey space-use dynamics. In tree crickets,
 Oecanthus henryi, mate searching involves acoustic signalling by immobile
 males and phonotactic movement by females. Space-use patterns in tree
 crickets relative to their primary predators, green lynx spiders (Peucetia
 viridans), should therefore depend on their current mate-searching state;
 whether males are calling or non-calling and whether females are
 phonotactic or non-phonotactic. We first measured the degree of spatial
 anchoring of crickets to specific bushes in the field, and whether that
 influenced the probability of broad-scale spatial overlap with spiders. In
 the absence of spiders, all crickets, independent of sex or male calling
 status, were found to be spatially anchored to specific types of bushes
 and not uniformly distributed on the landscape. At the broad spatial
 scale, spiders were more likely to be found on bushes with female
 crickets, and to a lesser degree, calling male crickets. At a finer
 spatial scale within a bush, movement strategies of crickets not only
 varied depending on the presence or absence of a spider, but also on their
 current mate searching state. Phonotactic females showed clear predator
 avoidance, whereas calling and non-calling males moved towards the spider
 instead of away, similar to predator-inspection behaviour seen in many
 taxa. As the strongly-selected sex, males are more likely to undertake
 risky mate searching activities, which includes inspection of predator
 positions. Overall, we found that all crickets were predictably anchored
 at the landscape scale, but their sex and mate seeking behaviour
 influenced the degree of overlap with predators, and their antipredator
 movement strategies. Reproductive strategies within a prey species,
 therefore, can alter predator-prey space race at multiple spatial scales.
description: Broad-scale space use Broad-scale space use
 of crickets and spiders was examined by performing field observations
 between 1900 hours and 2115 hours in the Ullodu (Karnataka, India) field
 when <em>O. henryi</em> are active in natural populations. We
 assessed whether spiders spatially overlap with crickets by comparing
 spider occurrences on bushes with crickets present and absent. For
 sampling ‘cricket-present’ bushes, we first localised crickets in the
 natural environment, either by their calls or using a combination of 5x5
 metre quadrat sampling and opportunistic searches. Once localised, all
 crickets were observed for a minimum of 30 minutes and assigned to
 specific categories depending on their mate searching behaviour. Males
 that were calling more than 20% of the time were classified as ‘calling
 males’ (N = 35 found), as opposed to ‘non-calling males’ (N = 42) which
 did not call at all. The 20% cut-off was chosen to avoid infrequent
 callers. Since there was no definitive way to categorise female behaviours
 from field observations, we did not further classify females as
 ‘phonotactic’ or ‘non-phonotactic’ at this scale (N = 43 females found).
 All crickets were caught, marked using nontoxic paint markers with a
 unique tricolour code, and released on the same bush to avoid resampling
 on successive nights. For sampling ‘cricket-absent’ bushes, we then
 randomly chose a bush that was at a distance (within 0.5 m to 10 m, at
 multiples of 0.5 m) and angle (from 0 to 360 degrees, at multiples of 3
 degrees) from each ‘cricket-present’ bush. All cricket-present (N = 120
 total) and cricket-absent (N = 145 total) bushes were carefully searched
 for the presence of spiders after the observation period, and if found,
 spiders were caught and their size measured to confirm their ability to
 capture crickets (Torsekar et al. 2019). This method ensured that we are
 searching for spiders in both cricket-present and cricket-absent bushes at
 approximately the same time in the night, avoiding any sampling errors
 assuming spider movement between bushes within a night.
 Fine-scale space use Fine-scale space use
 patterns were studied by comparing movement decisions of crickets within a
 bush when a spider was present (predator trials) and when absent (control)
 in outdoor enclosures. Crickets and spiders were collected from wild
 populations in and around Peresandra, Karnataka, India
 (13°35'25.3"N 77°46'50.4"E). All spiders were starved
 for 48 hours before the trials to ensure similar levels of predator
 motivation (Torsekar et al. 2019). For all trials, one cricket was
 released on a bush at 1500 hours and allowed 4 hours to habituate.
 Fine-scaled movement observations started at 1900 hours and ended at 2100
 hours. All categories of crickets were tested: calling males  (N = 29),
 non-calling males  (N = 40), phonotactic females (N = 42), non-phonotactic
 females (N = 32). Male crickets that called more than 20% of the time
 between 1900-2100 hours were categorised as ‘calling males’ and those not
 calling were ‘non-calling males’. To stimulate a phonotactic female, we
 played conspecific male calls from a speaker positioned 60 cm away from
 the female’s position. Calls were played continuously during the trial and
 only trials in which females elicited a phonotactic response and
 approached within 20 cm of the speaker were included in the ‘phonotactic
 females’ category. For the non-phonotactic female category, speakers were
 present but silent, and thus did not elicit the movement of
 females. For all four categories of crickets, we
 measured fine-scaled movement responses in the presence and absence of a
 predator. For predator trials, one spider was released at 1900 hours. For
 control trials, a spider-sized part of a bush branch was arbitrarily
 tagged as the reference for cricket movement measurements. For the
 predator trials, the cricket and spider were alternately scan-sampled
 every 30 sec, for a total of about 120 minutes, and all movement decisions
 by both were recorded as a change in direction relative to the previous
 location. After each trial, points of direction changes were sequentially
 numbered on the bush and converted to polar coordinates from a fixed
 reference point. This involved measuring the height from the ground, as
 well as the distance and angle subtended between each tagged point and the
 reference point. The reference point, common for all tagged points on a
 bush, was the centre of a fixed and levelled survey precision compass
 (Survey Compass 17475780, conceptualised by Francis Barker and Sons Ltd.,
 sold and serviced by Lawrence and Mayo, India). The subtended angles were
 measured using the survey precision compass, and the distances and heights
 were measured using a metre tape. The same procedure was followed for
 control trials, with the location of crickets sampled every 30 sec, for a
 minimum of 45 minutes.
description: Broad scale data includes 4 different categories:
 Bushes with calling males present (C)
 Bushes with non-calling males present (NC)
 Bushes with females present (F)
 Cricket-absent bushes (E) Column
 'cooc' contains data on whether a green lynx spider was present
 on the bush (1) or not (0). Space use data at the
 <strong>fine scale</strong> is uploaded separately for males
 crickets (calling and non-calling) and females (phonotactic and
 non-phonotactic). Each file has 4 different treatments:
 Calling males with predator present (CE) and absent
 (CC) Non-calling males with predator present (NCE)
 and absent (NCC) Phonotactic females with predator
 present (PE) and absent (PC) Non-phonotactic females
 with predator present (NPE) and absent (NPC) 
 Turning angles (labelled as 'angle') of each cricket
 were measured as the angle subtended between the present location of a
 cricket and the next location of the cricket relative to the current
 location of the spider. The distance between the cricket and spider when
 this movement was recorded is labelled as 'distance'. 
 Similarly, the time at which this movement was recorded is labelled as
 'time' and the respective cricket and spider identitfy is
 labelled as 'male.id' and 'gls.id'
 respectively.