DOI: 10.5061/dryad.3xsj3txjr
title: Western Diamondback Rattlesnake interaction matrices for network analysis

description: Social network ecology is a powerful framework to assess patterns of
 interconnectedness and identify group-level interactions. We investigated
 social network structure in a pitviper (Crotalus atrox) to determine if
 group-level interactions result in network structures for denning,
 pairing, and parentage. We tested if network centrality was influenced by
 body length, sex, home range size/location, or generic relatedness. We
 revealed that networks were structurally modular but not nested. Sex was
 the only significant predictor of centrality in the parentage network,
 likely due to high levels of multiple paternity. Genotypic data revealed
 interacting focal individuals were unlikely to be related in networks;
 however, analysis of a larger group of subjects suggests kin-association
 at communal dens. Den selection may be driven by a combination of social
 preference, experience, and/or genetic relatedness. We demonstrated strong
 fission-fusion dynamics connected to annual migrations to summer home
 ranges and use of communal winter dens. Furthermore, both sexes show high
 fidelity to home ranges and dens, but females occasionally alter den
 sites, indicating active manipulation of their social environment. Our
 study illustrates that comprehensive, long-term datasets incorporating
 social network analysis with spatial and genetic information provide
 robust and unique insights to understanding social structure of
 understudied, cryptic taxa.
description: Animals selected for this study were typically collected at or
 near known communal dens during egress in spring (March–April). The
 presence and location of communal rattlesnake dens at the Suizo study site
 has been known for nearly three decades and reported earlier. All other
 snakes we processed in this study were collected in late spring and summer
 (May–September) when they were dispersed in their home ranges.  
 Subjects were captured using conventional snake hooks and plastic
 grabbers. The capture process, which involved grabbing a snake and placing
 it into a clear plastic tube for temporary restraint (1 m length; diameter
 varied in size), was done gently and typically required less than 1 min to
 minimize handling stress. At the time of capture Global Positioning System
 (GPS) coordinates were collected as Universal Transverse Mercators
 (UTMs). Within 24-h of their initial capture, all
 subjects were measured (snout-vent length, tail length, head dimensions to
 the nearest millimeter; body mass to the nearest 1.0 g) and sex confirmed
 (via probing) while under light anesthesia (isoflurane). For subsequent
 identification, individuals were photographed, implanted with a unique
 PIT-tag (AVID, Inc., Norco, California, U.S.A.), and their proximal rattle
 segments were colored using Sharpie pens. A subset or
 focal group of adult <em>C. atrox</em> were collected from
 2001–2010 and used in the social network analysis (n = 50 focal animals;
 22 males 28 females). These subjects were selected for radio-tracking
 based on their size (e.g., 800 mm SVL or larger) and general state of
 health. Each animal had an appropriately sized (5% or less of their total
 body mass) temperature-sensitive radio-transmitter (models SI-2T and
 AI-2T, 11-16 g; Holohil Inc., Carp, Ontario, Canada) surgically implanted
 within the coelom following general procedures used for snakes. After
 processing, all subjects were released at their exact capture site (e.g.,
 communal den). Over the course of the study, we
 radio-tracked the snake subjects minimally 2–4 times per month including
 during winter. Tracking was increased substantially—sometimes daily or
 twice daily—from early August through mid-September, the period of
 birthing. For each radio-tracked subject located, UTM coordinates were
 recorded using a hand-held GPS unit. Other data recorded included
 behavior, body and environment temperatures, feeding and ecdysis status,
 plant associations, subject location (above or below the ground surface)
 and site number, visible or not visible, and health status.
 From these data, observational data were collected and converted
 to interaction matrices with individuals as rows and columns.