Live fast, die young: Life history traits of an apex predator exacerbate the ecological impact of a toxic invader

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 > 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 (> 20 adult li..., Data collection:
Radio telemetry
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, < 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 th..., , # 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 seve...