Relying on known or exploring for new? Movement patterns and reproductive resource use in a tadpole-transporting frog.

Kristina B Beck,Walter Hödl,Max Ringler,Andrius Pašukonis,Matthias-Claudio Loretto

doi:10.7717/peerj.3745

Kristina B Beck, Walter Hödl + Show 3 more

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https://doi.org/10.7717/peerj.3745

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Abstract

Animals relying on uncertain, ephemeral and patchy resources have to regularly update their information about profitable sites. For many tropical amphibians, widespread, scattered breeding pools constitute such fluctuating resources. Among tropical amphibians, poison frogs (Dendrobatidae) exhibit some of the most complex spatial and parental behaviors—including territoriality and tadpole transport from terrestrial clutches to ephemeral aquatic deposition sites. Recent studies have revealed that poison frogs rely on spatial memory to successfully navigate through their environment. This raises the question of when and how these frogs gain information about the area and suitable reproductive resources. To investigate the spatial patterns of pool use and to reveal potential explorative behavior, we used telemetry to follow males of the territorial dendrobatid frog Allobates femoralis during tadpole transport and subsequent homing. To elicit exploration, we reduced resource availability experimentally by simulating desiccated deposition sites. We found that tadpole transport is strongly directed towards known deposition sites and that frogs take similar direct paths when returning to their home territory. Frogs move faster during tadpole transport than when homing after the deposition, which probably reflects different risks and costs during these two movement phases. We found no evidence for exploration, neither during transport nor homing, and independent of the availability of deposition sites. We suggest that prospecting during tadpole transport is too risky for the transported offspring as well as for the transporting male. Relying on spatial memory of multiple previously discovered pools appears to be the predominant and successful strategy for the exploitation of reproductive resources in A. femoralis. Our study provides for the first time a detailed description of poison frog movement patterns during tadpole transport and corroborates recent findings on the significance of spatial memory in poison frogs. When these frogs explore and discover new reproductive resources remains unknown.

Highlights

In a dynamic environment resource availability changes in time and space which has major influences on animal movement decisions (Milner-Gulland, Fryxell & Sinclair, 2011; Bell, 2012)
If tadpole distribution over several sites improves offspring survival, knowing more pool locations should have direct fitness consequences. We speculate that this creates a trade-off between minimizing the costs of tadpole transport and maximizing the potential benefits gained through offspring partitioning over multiple learned sites. While it remains unknown when and how the poison frog A. femoralis collects information about the surrounding area, we provide, for the first time, detailed information about the movement patterns during tadpole transport
Despite extensive capture-recapture studies (e.g., Brown, Morales & Summers, 2009; Ringler, Ursprung & Hödl, 2009), and some tracking of A. femoralis after translocations (Pašukonis et al, 2014a; Pašukonis et al, 2014b) and tadpole transport (Pašukonis et al, 2016), still very little is known about the natural movement patterns of poison frogs and tropical amphibians in general

Summary

Introduction

In a dynamic environment resource availability changes in time and space which has major influences on animal movement decisions (Milner-Gulland, Fryxell & Sinclair, 2011; Bell, 2012). Animals that rely on unpredictable, ephemeral, and patchy resources have to explore their environment regularly (Roshier, Doerr & Doerr, 2008). Updating information on profitable resources can be achieved by exploring unknown areas to collect new information, by frequently visiting already known patches to affirm the availability of resources, or by prospecting for new resources within familiar areas (Real, 1981; Eliassen et al, 2009; Díaz et al, 2013). Animals depending on fluctuating resources need to find a balance between relying on known resources and prospecting for new ones (Milner-Gulland, Fryxell & Sinclair, 2011)

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