Growing evidence suggests that plant secondary compounds (PSCs) ingested by mammals become more toxic at elevated ambient temperatures, a phenomenon known as temperature-dependent toxicity. We investigated temperature-dependent toxicity in the desert woodrat (Neotoma lepida), a herbivorous rodent that naturally encounters PSCs in creosote bush (Larrea tridentata), which is a major component of its diet. First, we determined the maximum dose of creosote resin ingested by woodrats at warm (28–29°C) or cool (21–22°C) temperatures. Second, we controlled the daily dose of creosote resin ingested at warm, cool and room (25°C) temperatures, and measured persistence in feeding trials. At the warm temperature, woodrats ingested significantly less creosote resin; their maximum dose was two-thirds that of animals at the cool temperature. Moreover, woodrats at warm and room temperatures could not persist on the same dose of creosote resin as woodrats at the cool temperature. Our findings demonstrate that warmer temperatures reduce PSC intake and tolerance in herbivorous rodents, highlighting the potentially adverse consequences of temperature-dependent toxicity. These results will advance the field of herbivore ecology and may hone predictions of mammalian responses to climate change.
Kurnath et al R script expt 1
Code written in R to analyse data from the first experiment, determining the maximum dose of creosote resin in woodrats at two ambient temperatures. Specifically, the maximum dose for each individual was compared across temperatures with an ANOVA. Intake data was log transformed, averaged across all days in the trial per individual, and then ANOVAs were run with Tukey's post-hoc tests to determine the effect of temperature.
Kurnath et al R script expt 2
Code written in R to analyze data from the second experiment in the study, investigating the effect of temperature on the ability of woodrats to persist in a feeding trial while ingesting the same daily dose of creosote resin (ie, 0.36 g resin/day). There are two main parts to the code. First, we analyzed food intake and body mass data from animals at 25 and 29 degC, to determine if animals had similar energetic costs at these temperatures. Data was analyzed with ANOVAs. Second, we analyzed survival and intake (food and resin) from animals at three temperatures. Survival data was analyzed with a Kaplan-Meier test, and intake data was analyzed with ANOVAs and Tukey's post-doc tests.
Maximum Dose for Creosote Resin
Data spreadsheet used with "Kurnath et al Experiment 1" code in R, includes maximum dose for creosote resin of each individual in the study.
maxtol.csv
Daily Intake Data from Maximum Dose Trial
Data spreadsheet analyzed by "Kurnath et al Experiment 1" code in R. Each row represents one day of one animal in the feeding trial; there were 16 animals in the trial that lasted 21 days. Columns represent treatment groups (temperature, cool or warm), days in the trial, dietary concentration of creosote resin presented to the animals, body mass, food intake, creosote resin intake, and water intake of the animals during this experiment.
maxtol5.csv
Comparing energetic costs at two temperatures
Data spreadsheet analyzed by "Kurnath et al Experiment 2" code in R. Includes food intake and body mass data from animals at either 25degC or 29degC during a 6-day feeding trial.
rtdata.csv
Survivalship Analysis
Data spreadsheet analyzed by "Kurnath et al Experiment 2" code in R, includes animals at three temperatures and the number of days they persisted in a 10-day feeding trial.
R clipboard.xlsx
Intake data during Survivalship trial
Data spreadsheet analyzed by "Kurnath et al Experiment 2" code in R. Includes food intake, creosote resin intake, and body mass of animals at three temperatures during 10-day feeding trial. Each row represents one animal during one day of the trial. Columns represent temperature treatment, dietary concentration of creosote resin presented to animals, food intake, creosote resin intake, and body mass.
round3new2.csv