Consistently high temperatures have forced the University of Sydney to delay a chlamydia vaccine trial planned for Gunnedah's koalas.
The university's zoologist Dr Valentina Mella and veterinary pathologist Mark Krockenberger originally planned the trial for late January but recently made the decision to hold off until autumn.
"We are worried that the koalas are already stressed so we don't want to start the vaccine trial because we don't know if there are going to be any side effects. Sometimes their temperature can go up or they can feel funny," Dr Mella said.
"We don't want to add any stress so we prefer to leave it to April or May when it is cooler."
The heat has already resulted in koala deaths on Robert Frend's property where the university team has been carrying out research for a number of years.
One of the deceased koalas was originally part of their studies.
"We had captured the koala four times and it always came back negative for chlamydia, so it's not disease that has killed it, probably heat. It's very sad," Dr Mella said.
While the high heat has set back the trial, it provides the ideal environment to carry out a long-awaited temperature study this week to measure the effect of heat on the koalas and how water helps them to manage it.
About 30 koalas will be captured so the team can administer the capsules. The koalas will then be released and recaptured next week so the researchers can see how much water they've been drinking and how it has been used by the body.
The capsules measure the koalas' internal temperature over a period of time and from this data, the team can work out how hot koalas get before they become dehydrated. The data can be downloaded remotely.
Scanners on the property's water drinkers tell the researchers how often the koalas come to drink and for how long.
"We look for a relationship between the amount of time they spent at drinkers and body temperatures and water turnover," Dr Mella said.
"We record for as long as we can ... we know it comes out because the temperature changes suddenly from one minute to the other, so we know it has been excreted.
"We're hoping to find that koalas that are drinking have better thermal regulating ability than koalas that are not drinking."
It's the team's vision to be able to distribute water drinkers on a mass scale but they need the funding to do it, so they have relaunched a crowd funding initiative.
"There's an increase in the need to put water out for koalas ... [and] people know koalas need water and they're always willing to go a little bit to go out of their way to give them water," Dr Mella said.
- To donate to the water drinkers project, click here.