DOI: 10.5061/dryad.jwstqjqks
title: Data from: Live fast, die young: Life history traits of an apex predator exacerbate the ecological impact of a toxic invader

description: Abstract We studied a population of large varanid lizards (yellow-spotted
 monitors Varanus panoptes) on a floodplain in tropical Australia. Growth
 records from radio-tracked lizards show that despite their large adult
 body sizes (to &gt; 7 kg in males), these lizards attained sexual
 maturity at less than one year of age, and rarely lived for more than two
 years (females) or four years (males), even before mortality increased due
 to the arrival of toxic cane toads. This is a “faster” life-history than
 has been reported for other species of large monitors. Growth was
 especially rapid in males during the wet-season. The low survivorship
 prior to toad invasion was due to predation by pythons; communal nesting
 by female varanids may render them especially vulnerable. The life history
 of yellow-spotted monitors requires high feeding rates, favouring the
 evolution of “risky” tactics such as consuming novel prey items (such as
 cane toads); and the combination of high abundance (&gt; 20 adult
 lizards per square kilometre) and high feeding rates (&gt; 9.9 kg of
 prey per lizard per annum) means that these giant lizards play a critical
 role in energy and nutrient flow within the floodplain ecosystem. As a
 result, foodwebs with the yellow-spotted monitor as an apex predator are
 more vulnerable to disruption by cane toads than is the case in other
 parts of the toad’s invasive range, where the varanid species affected by
 toads have “slower” life histories.
description: <strong>Data collection:</strong>
 <em>Radio telemetry</em> Between
 November 2013 and January 2016 we radio‐tracked 110 yellow‐spotted
 monitors (Female lizards n= 52; Male lizards n= 58). During 15
 three-week-long field trips, we searched for monitors between 0500 h and
 1100 h each day; hence, new individuals were recruited to the study
 through time. By collaborating with indigenous rangers, we were able to
 collect lizards exhibiting a wide array of behavioural phenotypes
 (Ward-Fear et al. 2018, 2019). Monitors were captured
 by hand and transported back to the research station where we recorded
 snout‐to‐vent length (SVL) and body mass and took tissue samples from the
 tail tip for genetic sex determination (see Appendix for methodology). We
 attached a Very High Frequency (VHF) radio transmitter to the tail of each
 monitor (Holohil RI‐2B, 15 g, &lt; 5% total body mass) following the
 methods of Madsen and Ujvari (2009) and released the lizard back into the
 field at its point of capture within 6 h; telemetry began three days
 post‐release. We tracked monitors at least twice per field trip (but also
 opportunistically) for as long as they were alive and could be located
 (mean number of observations per individual 12.2, range 5–40
 observations). Throughout the study we opportunistically recorded
 information on behaviour, ecology and life-history attributes of the
 animals. <em>Calculation of growth rates and
 ages</em> We calculated growth rates using
 repeated measurements of snout-to-vent length (SVL) and body mass (g)
 taken on 17 males, 11 females and 4 hatchlings (total N = 32). Larger
 individuals were measured every three to six months, whereas juveniles
 were measured as often as possible. From the SVL measurements we
 calculated a von Bertalanffy (1957) curve to estimate growth rates (size
 vs age) <em>Reproduction and
 mortality</em> Over the course of the study we
 made 1,172 observations of radio-tracked monitors, only 7 of which were
 opportunistic encounters (i.e., a telemetered lizard was rarely sighted
 except by following the signal from its transmitter) plus 256 sightings of
 non-telemetered animals. We inferred sexual maturity for lizards seen
 mating or engaged in courtship, or seen at nesting warrens (GWF, unpubl.
 data). Gravid females were readily identifiable by their distended
 abdomens. We witnessed 27 instances of radio-telemetered individuals with
 mates, one full sequence of courtship then mating (lasting at least 4
 days), 13 instances of females nesting and an additional 18 instances of
 individuals thought to be engaging in mating and/or nesting in ‘warren’
 burrow systems. We also recorded 25 predation events on yellow-spotted
 monitors by pythons. <em>Energy requirements and
 rates of prey consumption</em> To estimate the
 annual rate of prey consumption by varanid lizards at Oombulgurri, we
 created energy budgets both on a per-individual basis and also for the
 annual offtake of prey by yellow-spotted monitors at our study site.
 Overall energy expenditure by an individual goanna during its annual
 period of activity (kJ per kg of goanna per day/month) was estimated as
 the sum of: (1) metabolic expenditure, from data on
 body mass (current study) combined with previous studies on mass-specific
 metabolic rates of active and inactive <em>V. panoptes</em> in
 a climatically similar site (Christian <em>et al.</em>
 1995); (2) allocation of energy to biomass growth, from
 growth rates in mass (calculated in the current study) combined with data
 on the energetic content of lizard tissue (Peterson et al. 1999);
 and (3) (for females only) allocation of energy to a
 clutch of eggs, based on mean clutch sizes and egg masses (from 6-14 eggs
 at 30-80gm each) and caloric content of eggs (5.8cal/mg – 7.2 cal/mg
 Tinkle 1975; Angilleta et al. 2001).
 <strong>Statistical Analysis:</strong>
 Normality and homogeneity of variance were confirmed for all
 variables. All continuous variables (age, number of days tracked, SVL,
 mass etc.) were transformed with natural log (Ln) prior to
 analyses. Seasonal growth rates - we
 ran full factorial ANOVAs with growth rates (i.e., the increase in mass
 between successive captures, standardised as gm/day) as our dependent
 variable, and independent variables of sex, season (wet = November to
 April; dry = May to October) and the interaction between the
 two. Reproductive age and survivorship
 - we analysed data on the age of all telemetered individuals
 that were recorded as mating or nesting during the study. The dependent
 variable in our ANOVA was the inferred age of the animal at the time of
 mating (obtained from the von Bertalanffy growth curve at initial capture
 and adding number of days tracked to that point) and the independent
 variable was sex (male/female). To explore sex differences in
 survivorship, we conducted ANOVAs to compare the mean number of days
 animals were tracked alive and the inferred ages of those animal at their
 time of death. We then created a population profile by
 calculating probable age at first capture from body size (using the von
 Bertalanffy growth curve then adding the number of days that the animal
 was tracked until it died). We used ANOVA to compare the average ‘ages’ of
 males and females within the population, as well as the distribution of
 age classes between the sexes.
description: # Live fast, die young: life history traits of an apex predator exacerbate
 the ecological impact of a toxic invader.
 [https://doi.org/10.5061/dryad.jwstqjqks](https://doi.org/10.5061/dryad.jwstqjqks) ## Description of the data and file structure This data was collected through an intensive radio telemetry project with the species in question, *Varanus panoptes.* The study was conducted in the Kimberley region of tropical Australia, specifically on a floodplain at Oombulgurri, to investigate the ecology and life history of the yellow-spotted monitor (*Varanus panoptes)* in a wet-dry climate. The research focused on understanding the impacts of cane toads on monitor populations, particularly mortality rates and age distribution. Data collection included radiotelemetry tracking of 110 monitors to assess growth rates, reproductive behaviors, and prey consumption, while also estimating population density and abundance through direct sightings and captures. The study was divided into several components: measuring growth rates using snout-to-vent length (SVL) and body mass, documenting reproductive activities such as mating and nesting, and analyzing energy budgets to estimate annual prey consumption. Additionally, comparisons were made between the yellow-spotted monitor and the sympatric lace monitor (*Varanus varius*) to evaluate the long-term effects of cane toads on both species. The research provided valuable insights into the ecological role of yellow-spotted monitors as a keystone species in their floodplain habitat, along with contributing to conservation strategies in light of invasive species impacts. ### Files and variables #### File: LFDY\_Data.xlsx **Description:** This is an excel file with data presented across two spreadsheets. The first spreadsheet includes all raw morphometric data for individuals and the second spreadsheet includes the metabolic rate calculations. The second sheet is partially a dataset and partially a set of calculations and also tabular format. It can't be put directly into analysis software without taking out the calculations. there are many cells where a label of 'no data' was given to pass tabular checks. after getting the dataset, remove these labels from cells for a clearer working spreadsheet.  ##### Spreadsheet 1: Morphometric and age data ##### Variables * ID number - the individual identification number assigned to individual goannas * Include in first caps - this is a sorting variable used to identify the first capture event (used in some analysis) anything '0' is an additional capture event for an animal - some analyses exclude these events, where as growth rate calculations required data from multiple captures over time. * SVL (mm) - this is Snout to Vent Length - a standardised measurement in millimetres taken along the ventral side of the lizard, from the tip of the snout to the urogenital opening underneath the pelvic girdle. This is a better measure than 'total length' which can change depending on tail malformation. * Net mass (gm) - this is the weight of the lizard in grams. * Gen. sex. - the gender of the lizard as identified by genetic determination from tissue samples. * Age - this is the age (in days) at the time of the respective capture event, calculated from a Bon-vertelanffy growth curve which determines age from size. ##### Spreadsheet 2: Metabolic calculations ##### Variables * sex - gender of lizard * days age - age of lizard in days at first capture * month of age - age of lizard in months at first capture * starting body mass - weight of each lizard at first capture * second days age - age of lizard in days at last capture * month 2 - age of lizard in days at last capture * finishing weight - weight at last capture * ∆ months - change in months between time points * ∆ weight - change in weight (gm) of each lizard between time points * change in weight per month - change in weight of each lizard per month * early wet/wet/dry/late dry - relate to teh seasons of teh year in tropical Australia and teh calculations based off previous research - which is referenced in the spreadsheet. * Column R - Y - these are additive metabolic costs for lizards which make up their metabolic requirements (eg. growth, reproduction, maintenance) and create a monthly expenditure in kilojoules (kj - column Y). * Column AD - AO - these are descriptive averages across our population based on season, sex etc. Remove all 'no data' label in cells to see more clearly. ## Code/software We ran our analyse in JMP 17. ## Access information Other publicly accessible locations of the data: * directly with the corresponding author: [georgia.ward-fear@mq.edu.au](mailto:georgia.ward-fear@mq.edu.au)