DOI: 10.5061/dryad.mw6m90656
title: Weathering the storm for love? The mate-searching behaviour of wild male Sydney funnel-web spiders (Atrax robustus)

description: The risky business of mate-searching often leaves the actively searching
 sex facing threats and rapidly changing conditions. Yet, active
 mate-searching behaviour is rarely studied in invertebrates, and we have
 limited understanding of how mate-searching strategies have evolved to
 cope with risks posed by harsh weather. We investigated how mate-searching
 males move through their habitat and how their movement is affected by
 weather conditions in the Sydney funnel-web spider (Atrax robustus), one
 of the world’s most venomous spiders. As is common in mygalomorphs
 spiders, females are functionally sessile, and are thought to spend their
 whole lives in a single burrow, whereas males must permanently abandon
 their burrows to mate during the breeding season. Nineteen male spiders
 were fitted with micro-radio transmitters and tracked during their mating
 seasons in 2020 (n = 2), 2021 (n = 8) and 2022 (n = 9) in Lane Cove
 National Park, in Sydney, Australia. Males moved at night, typically in a
 zig-zag pattern, and were found in new locations on approximately 50% of
 daily resighting’s. Males often spent several days in a female’s burrow,
 and some female burrows were visited by multiple males. When outside a
 female’s burrow, males constructed and occupied temporary shelters
 (‘temporacula’). Males were most likely to move and/or moved furthest when
 there was no rain, and on warm nights after cool days. Our findings
 suggest that mate-searching A. robustus males prefer to search for females
 in less risky conditions, revealing novel risk-minimizing strategies,
 especially in response to rainfall and temperature.
description: <em>Collection of wild spiders</em>
 This study was conducted on Eora and Kuring-gai (also Guringai)
 Nations’ lands. Individual male <em>Atrax robustus</em>
 specimens (n = 19) were collected between February and April of 2020 (n =
 2), 2021 (n = 8), and 2022 (n = 9), from Lane Cove National Park (-33.761,
 151.106), Sydney, Australia. To collect males, trips on foot after 8pm
 AEST were made along multiple fire trails within the national park. Males
 were spotted on and alongside the fire trail in undergrowth and upon
 elevated roadside banks. Collecting individuals involved placing an open
 500ml plastic container over the top of the spider, then encouraging the
 spider to walk into the container using the lid. Once collected, we
 labelled the location using flagging tape and saved the GPS location of
 each individual using a Garmin GPSMAP 62sc.
 <em>Transmitter attachment
 </em> We used model T15 micro-radio
 transmitters (Advanced Telemetry Systems, Gold Coast, Qld., Australia) to
 tag spiders (Figure 1). The T15 transmitters weigh 0.15 grams and are
 3.4mm x 11mm for the main body (Figure 1 A) plus a 150mm flexible antenna.
 Transmitters had a battery life of approximately 30 days. Two ATS R410
 scanning receivers with a 3-element folding yagi directional antenna were
 used to locate individuals with transmitters. At first
 capture, individuals were taken back to the lab at UNSW Sydney and
 photographed inside their container. In 2022, males were also weighed
 using a HT-120 compact balance (A&D Ltd., Thebarton, SA,
 Australia). Individuals were given a minimum of 12 hours to settle and
 were provided with water ad libitum before the transmitter was attached.
 Each ATS T15 transmitter was switched on using the ATS T15 controller app
 immediately prior to attachment to avoid battery life wastage. To attach
 the transmitters, each individual spider was placed into a 500ml plastic
 container with holes drilled into the sides and lid (Figure 1 B). A damp
 sponge was placed in the bottom of the container to ensure individuals did
 not desiccate. Once the individual was transferred to the container, the
 container was placed into a sealed plastic bag, which was then filled with
 CO<sub>2</sub> gas and sealed off for three minutes or until
 the individual was lethargic and easily manoeuvrable.
 The individual was them moved using forceps to the centre of the
 sponge (location marked with an X in Figure 1 B), and a second sponge (cut
 into a ring shape with a Perspex plate around the outside and two dowel
 rods attached to it) was placed over the top of the individual to ­expose
 the cephalothorax but restrain the legs and abdomen (Figure 1 B). A blunt
 size 28 tapestry needle was then used to smear a small amount of 430
 Loctite super glue (Henkel Corp., Ohio, USA) onto the cephalothorax and
 then onto the transmitter itself. Using fine point forceps, the
 transmitter was placed onto the cephalothorax and held there for
 approximately 15 seconds until the glue set. The cephalothorax was chosen
 as the site of transmitter attachment because it is a non-porous sclerite,
 whereas the abdomen is a membranous structure that expands and retracts
 and thus attempting to attach the transmitter on it would injure the
 spider. The top sponge was then removed, and the spider
 remained in the container for 30 minutes to allow the glue to cure
 further. The spider was then moved into its original container and allowed
 to recover for a minimum of 12 hours. During CO<sub>2</sub>
 exposure, the spiders did not elicit any signs of discomfort (Dombrowski
 et al., 2013). Each spider recovered normally in a dimly lit, quiet
 environment, and subsequent behaviour during the recovery period appeared
 normal. Only one fatality occurred using this procedure due to excess glue
 being applied. This individual was humanely euthanised using
 CO<sub>2</sub>. All other individuals were released in the
 location where they were found 12 – 48 hours after the transmitter was
 attached in the lab. In three cases, individuals were kept in the lab for
 seven days as they were collected immediately prior to the field site
 flooding and to ensure a safe release and safe field practices, we allowed
 extra time after the flood had passed.
 <em>Tracking of tagged spiders in the
 wild</em> Individuals were tracked one at a time
 every day using the receiver and antenna, unless extreme weather events
 prevented entry into the National Park. We recorded details of each
 individual on every day that they were tracked once the location of an
 individual was narrowed down to &lt; 1 square meter or the individual
 was sighted. In each case, we recorded a GPS coordinate and secured
 labelled flagging tape to foliage where the spider was located. We next
 measured the distance between the previous and current location (“nightly
 distance moved”) using a retractable 60 m measuring tape. If individuals
 were tracked to the same location and had not moved, this was recorded as
 a nightly distance moved of 0 m. If an individual had not moved and had
 not been physically sighted after three days, the site was thoroughly
 examined to ensure the transmitter had not dislodged or that the
 individual had not died. All males were tracked until either their
 transmitters dislodged (n=15), the transmitter ran out of battery (n=2),
 or the spider was found dead (n=2). The number of days of tracking and
 number of observations for each individual spider are shown in Table 1. If
 males were tracked into a burrow, the GPS coordinates of the burrow were
 recorded, and the individuals were left undisturbed. All males that were
 tracked into burrows subsequently re-emerged from the burrows.
 S<em>tatistical analysis
 </em> All statistical analyses were
 conducted using R version 4.3.1 (2023). Information on plant community
 types was obtained from the NSW State Vegetation Type Map (State
 Government of NSW and NSW Department of Climate Change, Energy, the
 Environment and Water, 2022) then layered over maps (configured in QGIS
 3.30.3) containing data on GPS locations for individual spiders.
 Temperature and rainfall data were obtained from The Australian
 Government, Bureau of Meteorology (Australian Government, Bureau of
 Meteorology, 2023). The data consist of minimum and maximum temperature
 and rainfall in all forms of precipitation recorded at 9am AEST, and
 therefore represent weather conditions for the preceding 24
 hours. Total distance travelled over the course of the
 season was calculated for each spider as the sum of its nightly movement
 distances, and the mean nightly movement distance was calculated by
 dividing the total distance by the number of nights when the spider moved
 to a new location. In addition, we estimated the linear projection
 (“displacement”) of each spider’s movement over the course of the season
 by measuring the distance between the first location of capture and the
 last location recorded in QGIS. To calculate how far on average each male
 moved per night away from the initial place of capture, we divided
 displacement by the number of nights between the date of release and the
 date of final observation (“mean nightly displacement”, Table 3). To
 quantify the linearity of movement, we then divided displacement by the
 total distance travelled (“displacement ratio”, Figure 2, Table 3). The
 displacement ratio would equal 1 if the spider moved in a straight line
 away from its location of capture, and 0 if the spider circled back around
 to its initial capture location. Because we had data on
 cephalothorax length and weight for different sub-sets of males, we tested
 for effects of both spider body weight and cephalothorax length (measured
 once at first capture) on mean nightly movement and mean nightly
 displacement using Pearson correlation analyses. Effects of environmental
 factors on nightly movement were analysed in two steps. First, we modelled
 a binomial variable (moved/not moved) to investigate the factors that
 affected whether spiders moved or stayed in the previous night’s location.
 Next, for spiders that had moved since the previous observation, we
 modelled a continuous (Gaussian) variable (nightly distance moved in m) to
 investigate the factors that affected how far spiders travelled while they
 were searching for mates. The binomial and Gaussian
 models both contained the following environmental parameters as fixed
 effects: daily rainfall (mm), nightly minimum temperature (ºC), daily
 maximum temperature (from the previous day; also, in ºC), and plant
 community type. The models also included fixed effects of year, and order
 of days tracked for each individual (each day tracked for each spider was
 given a number starting at 1 on day 1 and increasing in numerical order).
 Both models included individual identification and a code representing
 each day when tracking occurred as random effects. The correlation between
 minimum daily temperature and maximum daily temperature was weak (R =
 0.16), presumably because there was little seasonal change in average
 temperature during the time that spiders were tracked. We therefore
 included both the minimum and maximum daily temperature as fixed effects
 in our models. The plant community type (PCT) data obtained from NSW State
 Vegetation Type Map describes three broad habitat types present in Lane
 Cove National Park. These models were fitted using the TMB package
 (Kristensen, 2016). For both the binomial and Gaussian
 response variables, we carried out model selection based on Akaike’s
 information criterion corrected for small sample size
 (AIC<em><sub>c</sub></em>) using the MuMIn package
 (Barton, 2022). We compared models that included all combinations of fixed
 effects (without interactions) and intercept-only models (Kristensen,
 2016). All models included the two random effects, and diagnostics were
 assessed visually. Models with
 ΔAIC<em><sub>c</sub></em> &lt; 2 relative to
 the best-supported model (i.e., the model with the lowest
 AIC<em><sub>c</sub></em> value) were considered to
 have some support, whereas models with
 ΔAIC<em><sub>c</sub></em> &gt; 2 were
 considered to have very low support.
description: # Weathering the storm for love? The mate searching behaviour of wild
 males of (the Sydney funnel-web spider (Atracidae: Atrax robustus)
 [https://doi.org/10.5061/dryad.mw6m90656](https://doi.org/10.5061/dryad.mw6m90656) Authors: Caitlin N. Creak, Hugo Muirhead, Michael Kasumovic, Russell Bonduriansky, Bruno A. Buzatto Summary of Project: We investigated how mate-searching males move through their habitat and how their movement is affected by weather conditions in the Sydney funnel-web spider (Atrax robustus). Nineteen male spiders were fitted with micro-radio transmitters and tracked one at a time every day during their mating seasons in Sydney, Australia. We then compared their movement with temperature and rainfall data collected from the Australian Bureau of Meteorology. ## List of files **weathering_the_storm1.qmd**\ **Displacement.csv**\ **allspiders1.csv** ### File descriptions: **weathering_the_storm1.qmd** - The only file needed to see all analyses in manuscript. Loads in summary dataset and full dataset and runs the correlations, glmmTMB analyses, then runs the dredge and model selection. This can be opened in R studio as a Quardo Doc. **Displacement.csv**- A summary dataset for each individual spider Variables: *ID*: Identification code for each individual spider including the year *Total*: The sum of all meters travelled *Displacement*: Linear projection of each spider’s movement = distance between the first location of capture and the last location recorded. *Ratio*: Quantifying the linearity of movement, = displacement divided by total *Moved*: Number of times that individual moved throughout the study *Days tracked*: Number of days the individual had a transmitter attached *Name*: Field name of each individual *Weight*: Weight of individual in grams *Cephwid*: The cephalothorax width of each individual, measured at widest point, in cm *Cephleng*: The cephalothorax length of each individual, measured down centre of cephalothorax, in cm *Mean_disp*: Mean nightly displacement = displacement divided by Days tracked *Mean_meters*: Mean nightly movement + total distance divided by Moved Missing values: Displacement M3.20, potentially inaccurate GPS coordinates so omitted from the displacement analysis Ratio M3.20, as above Weight Scales only procured for the 2022 season, M4.22 had measurement error so omitted weight Cephwid Only individuals that had a quality photo taken were measured Mean_disp M3.20 as above for displacement. **allspiders1.csv** - Full raw dataset of tracking and observations Variables: *ID*: Identification code for each individual spider including the year *day*: Day of the month the observation was recorded *month*: Month the observation was made *year*: Year the observation was recorded *name*: Field name of individual *order*: Order number of the day the individual was tracked *moved*: Whether the individual moved (1) or didn't move (0) for that observation *meters*: Distance (meters) between previous and new location *mintemp*: Minimum temperature (degrees Celsius) recorded of the previous night *maxtemp*: Maximum temperature (degrees Celsius)recorded of the previous day *avtemp*: Average temperature (degrees Celsius) of the previous 24 hours = mintemp + maxtemp/2 *rain*: Total precipitation measured for the previous day (mm) *burrow*: Whether an individual was confirmed inside the burrow of a female (Y/N) *plantcom*: Plant community type, has four categories *caldate*: Number of day since tracking began, starting at 1 at the beginning of each year *caldatecat*: Number of day since tracking began + year code A = 2020, B = 2021, C = 2022 *latdecimal*: Decimal of the latitude the observation was recorded at *londecimal*: Decimal of the longitude the observation was recorded at Missing values: meters 19 missing values. Missing measurements due to park closure during floods or unsafe conditions. Addressed in the gaussian glmmTMB by removing all observations that have missing values. latdecimal 23 missing values due to GPS error, these values were either removed or manually adjusted in QGIS but are not used in the statistical analysis. londecimal Same as latdecimal Environmental data (Minimum temperature, Maximum temperature and rainfall) was obtained from the Australian Government Bureau of Meteorology ## Software R version 4.4.0 (2024-04-24 ucrt) R packages used: cowplot (version 1.1.3): Streamlined Plot Theme and Plot Annotations for 'ggplot2'.\ MuMIn (version 1.47.5): A package that contains functions carry out model averaging based on information criteria.\ tidyverse (version 2.0.0): A collection of packages for data manipulation, exploration, and visualization in R.\ ggpubr (version 0.6.0): A system that for creating and customizing 'ggplot2'- based publication ready plots.\ report (version 0.5.8): Automatic reporting of R objects.\ glmmTMB (version 1.1.9): Fits a generalized linear mixed model (GLMM) using Template Model Builder (TMB).\ DHARMa (version 0.4.6): Uses a simulation-based approach to create readily interpretable scaled (quantile) residuals for fitted (generalized) linear mixed models.