behavioural observations

Abstract

Cleaner shrimps are ecologically important members of coral reef communities, but for many species, cleaner status (i.e. dedicated, facultative and mimic), clientele and ecological role remain unverified or described. On Caribbean coral reefs, the spotted ‘cleaner’ shrimp Periclimenes yucatanicus forms symbioses with sea anemones that may serve as cleaning stations for reef fishes. The status of this species as a cleaner is ambiguous: only a single in situ cleaning interaction has been reported, and in the only test of its efficacy as a cleaner, it did not effectively reduce parasite loads from surgeonfish. It has subsequently been hypothesized by other authors to be a cleaner mimic. We conduct a comparative investigation of cleaning behaviour between P. yucatanicus and the ecologically similar, closely related, dedicated cleaner shrimp Ancylomenes pedersoni in Curacao, Netherlands Antilles. We provide the first detailed field observations on cleaning behaviour for P. yucatanicus and test multiple behavioural expectations surrounding mimicry in cleaning symbioses. We found that P. yucatanicusregularly signals its availability to clean, client fishes visit regularly and the shrimp does engage in true symbiotic cleaning interactions, but these are brief and our video reflects a species that appears hesitant to engage posing clients. In comparison to A. pedersoni, P. yucatanicus stations had significantly fewer total visits and cleans, and 50% of all cleaning interactions at P. yucatanicus stations were shorter than 10 s in total duration. Our behavioural observations confirm that P. yucatanicus is a true cleaner shrimp; we reject the hypothesis of mimicry. However, investigation is needed to confirm whether this species is a dedicated or facultative cleaner. We hypothesize that P. yucatanicus has a specialized ecological role as a cleaner species, compared to A. pedersoni.

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 the 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. The 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 1 month. Taken together, our results provide strong evidence 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.

Abstract

Feeding wildlife as a tourist activity is a growing industry around the world. However,providing alternative food sources can affect wildlife ecology and behaviour. In this study,we combined animal-borne cameras onfive sub-adult green turtles (Chelonia mydas) from the Bahamas with a global review to directly assess impacts of provisioning on thebehaviour of an endangered marine species for the first time. Descriptive evidence from video footage, with videos included in the manuscript, showed that the tagged turtles spent 86% of their time in shallow water (<1.5 m) at a provisioning site. All individuals observed, both tagged and untagged, actively approached people and boats, with up to 10 turtles recorded feeding on squid offered by tourists at one time. During these feeding events, multiple accounts of atypical aggressive behaviour such as biting and ramming conspecifics were recorded. Furthermore, a review of online sources revealed the wide-spread significance of turtle feeding as a tourist activity in at least 20 locations within the global range of green sea turtles, as well as five locations with regular provisioning ofeither loggerhead (Caretta Caretta) or hawksbill (Eretmochelys imbracata) turtles. At the majority of the locations, turtles were fed animal matter such as fish scraps and squid. Although sample size limited quantitative analyses, we found indications of relatively high growth rates of two tagged turtles and low seagrass intake rates of all five tagged turtles.Therefore, our results emphasize the need to further investigate the impacts of turtle provisioning on natural foraging behaviour, ecosystem functioning as well as turtle growth rates and health implications. Supplemental feeding may increase habituation and dependency of turtles on humans with risks for turtle conservation. The innovative use of animal-borne camera technology may provide novel insights to behavioural consequences of human-wildlife interactions that can aid in the management and conservation of rare or endangered species