Reproductive behavior drives female space use in a sedentary Neotropical frog

Abstract

Longer-range movements of anuran amphibians such as mass migrations and habitat invasion have received a lot of attention, but fine-scale spatial behavior remains largely understudied. This gap is especially striking for species that show long-term site fidelity and display their whole behavioral repertoire in a small area. Studying fine-scale movement with conventional capture-mark-recapture techniques is difficult in inconspicuous amphibians: individuals are hard to find, repeated captures might affect their behavior and the number of data points is too low to allow a detailed interpretation of individual space use and time budgeting. In this study, we overcame these limitations by equipping females of the Brilliant-Thighed Poison Frog (Allobates femoralis) with a tag allowing frequent monitoring of their location and behavior. Neotropical poison frogs are well known for their complex behavior and diverse reproductive and parental care strategies. Although the ecology and behavior of the polygamous leaf-litter frog Allobates femoralis is well studied, little is known about the fine-scale space use of the non-territorial females who do not engage in acoustic and visual displays. We tracked 17 females for 6 to 17 days using a harmonic direction finder to provide the first precise analysis of female space use in this species. Females moved on average 1 m per hour and the fastest movement, over 20 m per hour, was related to a subsequent mating event. Traveled distances and activity patterns on days of courtship and mating differed considerably from days without reproduction. Frogs moved more on days with lower temperature and more precipitation, but mating seemed to be the main trigger for female movement. We observed 21 courtships of 12 tagged females. For seven females, we observed two consecutive mating events. Estimated home ranges after 14 days varied considerably between individuals and courtship and mating associated space use made up for ∼30% of the home range. Allobates femoralis females spent large parts of their time in one to three small centers of use. Females did not adjust their time or space use to the density of males in their surroundings and did not show wide-ranging exploratory behavior. Our study demonstrates how tracking combined with detailed behavioral observations can reveal the patterns and drivers of fine-scale spatial behavior in sedentary species.

Keywords: Allobates femoralis; Fine-scale movement; Home range; Poison Frog; Reproductive behavior; Space-use; Tracking.

Figure 1. Tag attachment.

Female A. femoralis equipped with a miniature reflector tag for HDF telemetry, fixed to a waistband that is fitted to the size of the individual. Photo credit: Andrius Pašukonis.

Figure 2. Female activity patterns throughout the day.

We calculated the mean distance traveled per hour of the day for each female and averaged it over all study subjects (‘mean daily activity’, n = 17). The mean activity throughout the day is shown for days without courtship (black), on the day of courtship initiation (red) and on the mating day (blue). The most frequent hour of courtship initiation is marked with a hollow star, the most frequent hour of egg deposition is indicated by a grey star.

Figure 3. Movement in relation to reproductive behavior.

(A) Females moved significantly more on days associated with reproductive events compared to days without courtship or mating (Linear mixed model, p = 0.0002). (B) Mating associated movement didn’t differ between the day of courtship start (red) and the mating day (blue) (paired t-test, p = 0.41).

Figure 4. Home range estimation.

Datapoints of a representative female (f20, 17 tracking days) are mapped to visualize the two applied models of HR estimation: the more conservative Minimum Convex Polygon calculation (MCP95) is shown dark grey while the HR estimation calculated with KUD95 is depicted in light grey. The KUD30 area was defined as center of use (striped).

Figure 5. Female trajectory.

Representative example (f18) of female trajectory with two centers of use. Centers of use (C1, C2) are striped (KUD30). HR area (KUD95) is shaded light grey. Relocalization points after tagging before reaching a center of use are shown in dark grey. Datapoints in the center of use are indicated in black, sallies to the surrounding are hollow, pre-mating movement is indicated with red and post mating movement until the next center of use is reached with blue dots. The same color code was used for the bar chart displaying the female’s time management. The oviposition site is indicated by a yellow star. Territories of surrounding males were estimated with the Voronoi approach and marked with a marssymbol.

Figure 6. Long term site fidelity represented with short term tracking.

MCP areas calculated from tracking and CMR dataset are shown for four females. MCP100 Polygons for the respective female from the two datasets always overlapped. CMR capture points are marked with a red cross, tracking points are shown as dots. Tracking MCP100 polygons are shown in plane colors (white, light grey, dark grey, green-grey) while corresponding CMR MCP100 are shown in the same color but with wavy fill.