Data and R code for "Social foraging in vampire bats is predicted by long-term cooperative relationships"

Data and R code for the manuscript "Social foraging in vampire bats is predicted by long-term cooperative relationships" by Simon Ripperger &amp; Gerald Carter. published first on bioRxiv.org<br>For an explanation of the analysis, see the R notebook file "00_read_first.html".<br>SubjectsSubjects were common vampire bats (Desmodus rotundus) including 27 wild-caught adult females that were tagged and released, and 23 previously captive females (17 adults and their six subadult captive-born daughters) that had spent the past 22 months in captivity and were then tagged and released back into their wild roost tree (see Carter et al., 2020; Ripperger et al., 2019). See supplement for details.<br>KinshipWe assumed that known mother-daughter pairs had a kinship of 0.5. To estimate kinship for all other pairs, we genotyped bats at 17 polymorphic microsatellite loci (DNA isolated via a salt–chloroform procedure from 3-4 mm biopsy punch stored in 80 or 95% ethanol), then used the Wang estimator in the R package ‘related’. See supplement for details.<br>Past cooperative interaction rates in previously captive batsTo measure cooperative relationships in the previously captive bats, we used previously published rates of social grooming and food sharing from experimental fasting trials (Carter et al., 2020). See supplement for details. To assess tolerance while feeding, we also analysed previously unpublished data on co-feeding among the same captive vampire bats. Social interactions were observed at blood spout feeders while the bats were in captivity, including 1300 competitive interactions and 277 cases of co-feeding where two bats were observed feeding from the same blood spout at the same time (from 1050 h of observation from 70 nights). We used 201 co-feeding events with identified bats to construct a co-feeding network of the number of dyadic co-feeding events (range = 0 to 6) for each pair.<br>To assess correlations between the captive co-feeding network and networks of food sharing or social grooming, we used Mantel tests. To test the same correlation while controlling for overlap in individual feeding times, we also used a custom double permutation test (Farine and Carter, 2020). This procedure calculates an adjusted co-feeding rate for each pair as the difference between the observed co-feeding rate and the median expected co-feeding rate from 5000 permutations of the co-feeding bat identities, permuted among the bats seen within each hour. The results of this constrained permutation test and the unconstrained Mantel test were similar and gave the same conclusion, so we report only the results from the double permutation test. To test for preferred captive co-feeding partners, we also used the same within-hour permutations to test if social differentiation in co-feeding (the coefficient of variation in co-feeding rates) was greater than expected from the null model.<br>Association rates in the wild using proximity sensorsWe placed custom-made proximity sensors on all 50 female common vampire bats (sensor mass: 1.8 g; 4.5-6.9 % of each bat’s mass) that automatically documented dyadic associations among all 50 tagged bats when those come within reception range (max. 5-10 m). To log encounters, each proximity sensor broadcasted a signal every two seconds to update the duration of each encounter. We used 1 s as the duration of encounters that were shorter than two successive signals (i.e., encounters shorter than two seconds). The maximum signal strength of each encounter can be used as an estimate for a minimum proximity between two tagged bats during the encounter by comparing the signal intensity to a calibration curve (Ripperger et al., 2019; Ripperger et al., 2020b).<br>We collected association data on the free-ranging bats at Tolé, Panama (8°12'03"N 81°43'46"W), a rural area that is mainly composed of cattle pastures for meat production. Around 200-250 common vampire bats roosted inside a hollow tree on a cattle pasture that was about 15 ha in size. To create a stable food patch, we corralled ca. 100 heads of cattle at a distance of ca. 300 m from the roost from 6pm until 6am between the evening of September 21 until the morning of September 26, 2017 (days 1 to 5 in our study). Before and after that time period, the cattle were ranging freely. A neighboring, much larger pasture west of the roost had about 1,500 heads of cattle within a distance of 1-2 km (Figure S1). <br>To construct networks of roosting association rates during each daytime period within the roost, we relied on roosting association data that had been used in a previous study (Ripperger et al., 2019). Based on the same two thresholds of signal strength as before, we defined two categories of proximity: “associations” (within a maximum of ca. 50 cm) and “close contacts” (within ca. 2 cm). Roosting network edges were rates of within-roost association or close contact, i.e. the total time two bats spent in association per unit of time. See supplement for details.<br>To log presence and co-occurrence of foraging bats at points outside the roost during the night, we placed base stations (which can detect tagged bats at distances of about 150 m) at the roost and at 5 other locations in the surrounding cattle pastures. To identify departures from the roost, we found the points in time where each bat lost connection from the roost base station and almost all of the many tagged bats in the colony within communication range (i.e., a sudden drop in associations from many bats down to 0-3 bats; see figure 2 in Ripperger et al. (2020b)). Departing bats may have also contacted base stations on the cattle pasture (Figure S1). We used the same kind of data to find the return times to the roost for each bat and night. <br>Of the 629 dyadic encounters that occurred one minute after leaving the roost and one minute before arriving at the roost, we excluded 43 encounters from further analysis, because a proximity sensor contacted the roost base station, suggesting that those encounters occurred while bats were roosting at the entrance or on the outside of the roost tree. The remaining 586 encounters occurred farther away, outside the communication range of the roost base station, and we refer to these as “foraging encounters”.