Responding to heat stress in flying-fox camps
Heat stress affects flying-foxes when temperatures reach 42°C or more. Over the past two decades, a number of documented heat stress events have resulted in significant flying-fox mortality.
While there is conflicting advice about how or whether to intervene during a heat stress event at a flying-fox camp, it should be noted that human presence in a camp at such times can increase the stress and activity levels of flying-foxes present, potentially leading to greater harm.
The following advice is provided for people who choose to respond to heat stress events in flying-fox camps, which should be undertaken as an organised and monitored response. It is recommended that data is collected after the heat stress event and provided to scientists able to analyse the data and to help the Office of Environment and Heritage share best practice management techniques as they are developed. The data collected will help improve future advice on intervention during these events.
What is heat stress?
Heat stress or hyperthermia occurs when the body produces more heat than it can dissipate. Post-mortems suggest that flying-foxes mainly die from resulting heat shock i.e. the body can no longer function effectively.
How can I tell whether flying-foxes are affected by a heat stress event?
When ambient temperatures rise above 35°C flying-foxes tend to alter their behaviour to reduce exposure to heat. A range of behaviours may be exhibited, depending on multiple variables in their environment. The impacts of heat stress events are likely to vary site by site, and can depend on conditions in the preceding days. Ambient temperature alone may thus not be a sound indicator of a heat stress event, and flying-fox behaviour may provide more reliable information. As flying-foxes experience heat stress, they are likely to exhibit a series of behaviours indicating progressive impact of that stress, including clustering or clumping, panting, licking wrists and wing membranes, and descending to lower levels of vegetation or to the ground. Some of these behaviours may occur outside of heat stress events.
Black Flying-foxes tend to start dying above ~42°C, and Grey-headed Flying-foxes above ~43°C.
What factors affect the severity of heat stress on flying-foxes?
Impact is likely to be reduced by the presence of:
- understorey and mid-storey vegetation so that flying-foxes can shelter from heat
- dense crown vegetation to provide shade
- access to water.
Impact is likely to be increased when camps are disturbed at critical times during a heat stress event, potentially forcing individuals to leave their cooler microhabitats and become fully exposed to the extreme heat.
Do I need approval to help flying-foxes during a heat stress event?
Yes. You will need to be licensed to rehabilitate fauna under the National Parks and Wildlife Act 1974. You may be licensed as an individual or be a current member of a licensed fauna rehabilitation group. Alternatively, you have a job which lawfully entitles you to intervene in animal welfare issues (e.g. with the council, Department of Primary Industries, Office of Environment and Heritage including National Parks and Wildlife Service, RSPCA or you are a registered veterinarian). In either case, the licence or role must specifically endorse the person or group as being able to care for flying-foxes. If you are not sure about your coverage under a current licence, contact your local fauna rehabilitation group or, for individual licences, the Biodiversity and Wildlife Team in Office of Environment and Heritage on 9585 6404 or at Wildlife.Licensing@environment.nsw.gov.au.
A requirement of being licensed is that you must be immunised against Australian Bat Lyssavirus (ABLV) and you will need to source and wear suitable protective equipment and clothing. It is also recommended that you undertake training in handling flying-foxes. See more information on licensed rehabilitation groups.
The Code of practice for injured, sick and orphaned protected fauna is designed for those involved in the rescue, rehabilitation and release of native fauna and outlines how they can protect the welfare of the animals in their care. The Code contains both standards and guidelines for the care of native animals that are incapable of fending for themselves in their natural habitat. Compliance with the standards is a condition of all Office of Environment and Heritage rehabilitation licences. If groups intend to take action in heat events Office of Environment and Heritage encourages prior planning to ensure that the group has the resources necessary to meet the standards.
Office of Environment and Heritage has also produced a series of species-specific codes to complement the general code of practice, including a Code of practice for injured sick and orphaned flying-foxes (PDF 86KB). This code provides details on standards for rescue, transport, euthanasia, care procedures, husbandry, housing and release.
If I am a licensed fauna rehabilitator do I have a right to enter someone's property to aid flying-foxes during a heat stress event?
Access to sites where animals are affected needs to be negotiated with the relevant land holder.
For national parks refer to the state duty officer (9895 6444).
For Crown Lands refer to customer service during business hours (1300 886 235).
For state forests refer to Forestry Corporation of NSW.
For council managed land check the relevant local council website for contact details.
Can I get approval to take heat-stressed flying-foxes interstate for rehabilitation?
Not immediately. Office of Environment and Heritage, specifically National Parks and Wildlife Service, cannot provide immediate approval to transport heat-stressed flying-foxes across state borders for care because of the potential biosecurity and health risks involved. Authorisation will also be required from other interstate agencies to approve the importation of animals. Securing these approvals takes time and may require testing of affected animals to establish their health status and quarantine requirements. Endeavours should be made to treat affected animals within NSW using the network of available fauna rehabilitators. You can contact the Biodiversity and Wildlife Team in Office of Environment and Heritage on 9585 6406 to discuss obtaining an import/export licence if needed.
Office of Environment and Heritage is working with other state jurisdictions to facilitate cross-state emergency measures for flying-fox rehabilitation in the future.
In the meantime, if injured flying-foxes are moved during a heat stress event for rehabilitation, they should be released in accordance with the fauna and flying-fox codes of practice.
Who do I call if I am concerned about flying-foxes being affected by heat stress?
People concerned about potential heat stress events on flying-foxes may report their concerns to a local fauna rehabilitation group or the RSPCA. Local councils or the Local Area National Parks and Wildlife Service Duty Officer can also be contacted. It may not always be possible or appropriate to intervene in such events depending on the circumstances. Intervention is not mandatory. It is recommended that wildlife carer groups develop an incident response protocol relevant to the local area that will be used by their members when flying-fox camps suffer heat stress.
If a heat stress event occurs outside of business hours, the National Parks and Wildlife Service state duty officer (9895 6444) may be able to assist with local contacts.
What to do during a heat stress event?
During a heat stress event, flying-foxes will likely occupy the coolest microhabitats available to them at that temperature, and disturbance may move flying-foxes into less desirable locations. Great care should be taken to avoid unnecessarily disturbing flying-foxes at this time.
General health and safety issues must be identified beforehand and appropriate measures implemented during the event.
Spraying animals in the camp
Spraying of specific individuals by hand can cool highly distressed animals. However, care must be taken not to disturb other flying-foxes, as this may cause them to leave the shelter of their relatively cool microhabitats and increase their body temperature, further stressing them.
Flying-foxes should not be approached if they show any indication that they are trying to move away or escape from the presence of the sprayer. Highly heat-stressed individuals that do not respond to spraying should be observed for 15 minutes before undertaking a second round of spraying. The individual may then be removed from the camp after a period of observation by an experienced wildlife carer for further treatment.
Removing animals from a camp and rehydration therapy
Animals that are severely affected by a heat stress event may need intensive cooling and rehydration. In some cases this may necessitate removal of the animal from the camp to a quiet and shady location.
People dealing with these animals must be vaccinated, wear protective clothing and have experience and training in administering fluid therapy.
After a heat stress event
If flying-foxes have died during a heat stress event, care should be taken to ensure domestic dogs and cats do not enter the camp. While preliminary research indicates the likelihood of cats and dogs becoming infected following contact with a bat infected with Australian bat lyssavirus (ABLV) is low, it is theoretically possible that a pet that contacted an infected bat could become infected with ABLV and could then transmit that infection to a human.
Collecting data about mortality and effectiveness of strategies
After the heat stress event is over, it will be important to collect information that can provide a better understanding of the nature and severity of heat stress events on flying-foxes, and contribute to more effective management responses to these events. Information should include observations of the camp during the heat stress event, what treatments were applied, numbers of each species present, and relevant injury and mortality data. Monitoring of the site in the days following the heat stress event will be important as flying-foxes may exhibit the impacts of stress for several days after the event.
When collecting these data, volunteers handling dead flying-foxes must be vaccinated against ABLV (with current titre) and wear personal protective clothing.
Download the Responding to Heat Stress in Flying-fox Camps - Monitoring Data Sheet (DOC 90KB).
Any dead flying-foxes which are banded should be reported to the Australian Bird and Bat Banding Scheme.
Having completed any mortality and post-mortem assessment, carcasses should be disposed of. As with any animal waste, flying-fox carcasses should be disposed of by people wearing appropriate protective clothing. Carcasses should be picked up using a shovel or by hand while wearing thick gloves, double-bagged and dropped at a registered landfill site. If you have concerns or questions about disposing of dead flying-foxes, contact your local council for advice on waste management in your area.
Completed data sheets should be sent to:
Dr Justin A. Welbergen
Senior Lecturer | Hawkesbury Institute for the Environment | UWS Hawkesbury Campus
Locked Bag 1797, Penrith, NSW 2751, Australia
Direct: +61 2 4570 1496 | Mobile: +61 4 5733 8189 | Fax: +61 2 4570 1103
Page last updated: 14 February 2017