DOI: 10.5061/dryad.h44j0zpms
title: Territoriality drives patterns of fixed space use in Caribbean parrotfishes

description: Animals often occupy home ranges where they conduct daily activities. In
 many parrotfishes, large terminal phase (TP) males defend their diurnal
 (i.e., daytime) home ranges as intraspecific territories occupied by
 harems of initial phase (IP) females. However, we know relatively little
 about the exclusivity and spatial stability of these territories. We
 investigated diurnal home range behavior in several TPs and IPs of five
 common Caribbean parrotfish species on the fringing coral reefs of
 Bonaire, Caribbean Netherlands. We computed parrotfish home ranges to
 investigate differences in space use and then quantified spatial overlap
 of home ranges between spatially co-occurring TPs to investigate
 exclusivity. We also quantified spatial overlap of home ranges estimated
 from repeat tracks of a few TPs to investigate their spatial stability. We
 then discussed these results in the context of parrotfish social behavior.
 Home range sizes differed significantly among species. Spatial overlap
 between home ranges was lower for intraspecific than interspecific pairs
 of TPs. Focal TPs frequently engaged in agonistic interactions with
 intraspecific parrotfish and interacted longest with intraspecific TP
 parrotfish. This behavior suggests that exclusionary agonistic
 interactions may contribute to the observed patterns of low spatial
 overlap between home ranges. Spatial overlap of home ranges estimated from
 repeated tracks of several TPs of three study species was high, suggesting
 that home ranges were spatially stable for at least one month. Taken
 together, our results suggest that daytime parrotfish space use is
 constrained within fixed intraspecific territories in which territory
 holders have nearly exclusive access to resources. Grazing by parrotfishes
 maintains benthic reef substrates in early successional states that are
 conducive to coral larval settlement and recruitment. Behavioral
 constraints on parrotfish space use may drive spatial heterogeneity in
 grazing pressure and affect local patterns of benthic community assembly.
 A thorough understanding of the spatial ecology of parrotfishes is,
 therefore, necessary to elucidate their functional roles on coral
 reefs. 
description: <strong>Study species and sites</strong>
 We conducted our research on <em>Scarus iseri</em>,
 <em>Scarus taeniopterus, Scarus vetula, Sparisoma
 aurofrenatum</em>, and <em>Sparisoma viride</em> at five
 fringing coral reefs along the leeward coast of Bonaire during January
 (Winter) and May-July (Summer) 2019: Angel City (12.10305º, -68.28852º),
 Aquarius (12.09824º, -68.28624º), Bachelor’s Beach (12.12605º,
 -68.28819º), Invisibles (12.07805º, -68.28175º), and The Lake (12.10618º,
 -68.29079º). The fringing coral reefs of Bonaire, Caribbean Netherlands
 have remained resilient despite multiple disturbances, and boast higher
 coral cover than most Caribbean coral reefs (Perry et al. 2013, Steneck et
 al. 2019). The abundance and biomass of different fish groups, including
 parrotfishes, is also much higher on Bonaire’s coral reefs compared to
 more heavily fished reefs in the Eastern Caribbean (Hawkins &
 Roberts 2003, 2004, Steneck et al. 2019). The benthic composition across
 our study sites was similar, with relatively high coral cover (~20%) and
 low macroalgal cover (&lt; 3%; Manning & McCoy 2022).
 Additionally, our five focal parrotfish species comprised more than 96% of
 the parrotfish biomass at our study sites (Manning & McCoy
 2022). <strong>Parrotfish
 tracking</strong> We conducted concurrent GPS
 tracking and behavioral observations of TP and IP parrotfishes between
 1000–1600 hrs, peak foraging times for parrotfishes (Bruggemann et al.
 1994b a). We identified focal parrotfish (TP or IP) haphazardly at ~10 m
 depth on SCUBA at each site. Each fish was then allowed to acclimate to
 diver presence for approximately 1–2 mins, during which time we visually
 estimated standard length (to the nearest cm) by measuring the distance
 between reference objects passed by the fish using a collapsible
 meter-stick. We then estimated body mass (g) from standard length using
 published length-weight relationships (Bohnsack & Harper 1988;
 Appendix: Table A1). We followed focal fish from ~2 m, and recorded their
 behavior in high resolution (4K) using a GoPro Hero 4 Silver (GoPro, Inc)
 attached to a ‘selfie-stick’. <br><br>Focal parrotfishes were
 tracked at the surface by a snorkeler carrying a handheld GPS receiver
 (Garmin GPSMap 78sc, United States of America) for 13.56 ± 0.19 mins (mean
 ± SE, n = 215 total tracks). The GPS receiver was set to record data as
 often as possible, resulting in a mean (± SE) relocation interval of 12.32
 ± 0.21 s (mean ± SE, n = 215 total tracks). We ensured that we did not
 track the same individuals unintentionally by progressively moving north
 along the reef, using reference structures, until we identified another
 unique individual to observe. A few times, we unintentionally conducted
 repeat tracks of previously tracked individuals (on the same day or within
 a few days; confirmed as described below). In such cases, unintentional
 repeat tracks were excluded from our analyses. Because our interest was in
 the home range behavior of territorial fishes, we excluded
 non-territorial, transient TP fishes from our analyses. Transient,
 non-territorial TPs were not site attached and were frequently chased
 along the reef by territory holders. <br><br>We preliminarily
 tracked several territorial TP (hereafter, just TP) <em>Sp.
 viride</em> at two sites in Winter 2019. Then, during Summer 2019,
 we tracked several TP <em>Sc. taeniopterus, Sc. vetula,
 </em>and<em> Sp. viride</em> at all five sites, and TP
 <em>Sc. iseri </em>and <em>Sp. aurofrenatum
 </em>at two sites. To investigate differences in space use among
 ontogenetic phases, we also tracked IP <em>Sc. taeniopterus, Sc.
 vetula, </em>and<em> Sp. viride</em> at two sites during
 Summer 2019. Finally, to quantify short-term spatial stability of
 parrotfish home ranges (described below), we conducted planned repeat
 tracks of several TP <em>Sc. taeniopterus, Sc. vetula,
 </em>and<em> Sp. viride </em>at two sites during Summer
 2019. Repeat tracks were obtained by tracking TPs along the same portions
 of the reef where they had been tracked ~1 month prior. Individual
 parrotfish are identifiable by unique color patterns and markings on their
 bodies (Dubin 1981, van Rooij et al. 1996). We compared color patterns and
 markings of each fish using stills taken from our video recorded
 behavioral observations to confirm that initial and repeat tracks were of
 the same fish and not different fish occupying the same areas (Figures
 A1-A3). We also obtained unplanned, repeat tracks of 4 TP <em>Sp.
 viride</em> at Angel City and Bachelor’s Beach (n = 2 per site)
 during Summer 2019 that were initially tracked in January 2019. Home
 ranges of the 4 fish were in the same locations in both tracking periods,
 and visual observation of color patterns and markings from video stills
 confirmed that they were the same fish. A full breakdown of our sampling
 effort is reported in the Appendix (Table A2).
 <br><br><strong>Home range
 estimation</strong><br><br>Visual analyses of
 stationarity confirmed that our GPS tracks were sufficiently long to
 capture home range behavior (Figure A4; Benhamou 2014). We used
 movement-based kernel density estimation (MKDE) to estimate utilization
 distributions from our tracks of individual parrotfishes (sensu Benhamou
 2011), and define home range and core use areas as the areas underneath
 the 95% and 50% cumulative isopleths of each utilization distribution,
 respectively. Though we used MKDE estimates of home ranges for analyses of
 space use in our study, we also present home range sizes estimated using
 traditional location-based kernel density estimation (ad hoc bandwidth
 selection) and minimum convex polygons to facilitate comparisons of home
 range area with other studies (Table A3). All home ranges and core use
 areas were computed in the <em>adehabitatHR</em> package in R
 (Calenge 2006, R Core Team 2020).<br><br><strong>Home
 range exclusivity and stability</strong><br><br>To
 investigate the exclusivity of parrotfish HRs, we quantified spatial
 overlap between HRs of spatially co-occurring TP parrotfishes tracked
 during Summer 2019. This measure of spatial overlap estimates shared space
 use between neighboring fish that are sharing at least some space on the
 reef. We used only HRs estimated from the first GPS track of TPs for which
 we had replicate GPS tracks. Spatial overlap was estimated using
 Bhattacharyya’s Affinity (BA), a function of the product of two
 utilization distributions that ranges from 0 (no overlap) to 1 (perfect
 overlap) and is a strong metric of joint space use between animals,
 particularly when comparing utilization distributions estimated for the
 same animal at different times (Fieberg & Kochanny 2005). As such,
 we also used BA to quantify the spatial overlap of HRs estimated from
 repeat tracks of TP <em>Sc. taeniopterus, Sc. vetula</em>, and
 <em>Sp. viride</em> to determine the spatial stability of
 those HRs. To distinguish spatial overlap between different spatially
 co-occurring individuals and spatial overlap of home ranges estimated from
 repeat tracks of the same individuals, we use the terms spatial overlap
 and temporal overlap, respectively. Spatial and temporal overlaps of MKDE
 home ranges were computed in the adehabitatHR package in R (Calenge 2006).
 <br><br><strong>Occupancy
 change</strong><br><br>During our attempt to repeatedly
 track parrotfishes at Aquarius, we observed an occupancy change in a TP
 <em>Sc. vetula</em> home range. We analyzed this occupancy
 change as a separate case study (Figure A5). To investigate how a change
 in occupancy affected space use, we quantified spatial overlap between the
 home range of the new occupant and the home range of the old occupant. We
 also quantified spatial overlap between the home range of the new occupant
 and the home ranges of spatially co-occurring intraspecific and
 interspecific fishes from the initial tracking (Table
 A4).<br><br><strong>Social
 behavior</strong> We quantified the social
 behavior of the TP parrotfishes tracked in Summer 2019 (n = 128) by
 analyzing the video recordings of the initial tracks for each fish (when
 repeat tracks existed) in the behavioral software
 <em>BORIS</em> (v. 7.9.8; Friard and Gamba 2016). For each
 fish, we quantified the number of agonistic interactions they had with
 other parrotfishes, the identity (i.e., ontogenetic phase and species) of
 interacting parrotfishes, and interaction durations (s). In some cases, we
 were unable to determine the identity of the interacting parrotfish, and
 classified such interactions as ‘unknown’. Agonistic interactions between
 parrotfishes consisted of displays (i.e., extension of dorsal and pelvic
 fins) and more aggressive (and typically longer) chases that are
 characteristic of territorial behavior/aggression in parrotfishes
 (e.g., Buckman & Ogden 1973, Mumby & Wabnitz
 2002).  <strong>Literature cited in
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