When you think of bats, I am sure your first thoughts do not involve warm, cuddly feelings. Bats are typically viewed negatively in society as a symbol of darkness and carriers of disease, spreading rabies far and wide. Contrary to popular belief, less than 1% of Australian bats carry rabies (known as the Australian Bat Lyssavirus (ABL)). While the risks of transmitting the virus to humans are very low, bats have the capacity to host many other pathogens without symptoms, and this is largely due to their innate immune response. Meaning that they have evolved to coexist with many viruses without becoming ill, showing no or minimal signs of illness, even during high viral loads. There is increasing concerns for potential bat-human disease transmissions as land clearing is forcing bats to live closer and closer alongside humans as their roost sites are reduced.
Natural Ecological Pesticides
Bats are remarkable, providing essential ecosystem services such as long-distance pollination and seed dispersal of native Eucalyptus trees, as well as predating on agricultural pests. In fact, farmer’s may not even realise that these natural ‘ecological pesticides’ are living right in their own backyard, protecting their crops. Now, you might be thinking, how do bats help crop farmers? Wouldn’t we notice this happening?
Well, microbats are very small, weighing a mere mighty 3 to 150 grams, which is why you wouldn’t notice this happening in your very own backyard, and probably not what you envisioned when you heard the word bat. These tiny bats can consume up to 40-100% of their own body weight in insects each night; including a wide variety of insects, such as mosquitoes, moths, flies, beetles, and other various bugs. Their large consumption of insects affects population sizes of invertebrates, which not only benefits farming, but also tree health and pastures. Their whereabouts are rather cryptic due to their nocturnal lifestyle, small size, fast flight, and roosting preferences.
Bats enjoy roosting in a vast number of locations and a variety of places, such as within tree hollows, under bark and leaf litter, in stormwater pipes, sheds, caves and all sorts of crevice’s you would not expect to find a bat.
The bats serve an important ecosystem service to farmers by reducing insect pest populations. The natural pesticide properties that they provide is valuable to organic farmers. So valuable in fact, there have even been reports of organic farmers installing bat roosting boxes (a form of artificial habitat) throughout their farms to encourage natural pest control. Since pesticides can have harmful effects to the environment and are continuously declining in effectiveness, encouraging microbats in agricultural landscapes has never been so important.
Fun fact: Microbats can exhibit a short form of hibernation, known as torpor. A microbat’s normal body temperature range is 35-39°C, however, during torpor it can be as low as 2°C! By reducing their body temperature, they are able to conserve energy through food shortages and cold seasons.
Not only do they support pesticide control in a food farming environment, but the bats also forage for insects across a vast number of agricultural landscapes, including cotton farming; it is a bit batty to think that microbats might be the reason you have that shirt on your back. Biodiversity and farming go hand-in-hand, and by having a greater understanding of their interaction together means that we can invest in better conservation practices. It is imperative to recognise that even although agricultural landscapes have been highly modified, they can still provide valuable habitat to microbat communities.
Despite the bats ecological importance and due to their cryptic nature, microbats are in rapid decline from deforestation and are frequently overlooked in biodiversity assessments. Australia is in a deforestation crisis and is one of the worst offending countries in the world for mammal extinctions. In 2015-2016 approximately 395,000 hectares of vegetation was cleared, to put this into perspective, a conservative estimate of 1,000 trees per hectare is almost 400 million trees in that single year alone.
It is no wonder that microbats are declining, since they mostly prefer roosting in tree hollows and under bark, and are often not detected during tree felling due to these cryptic roosting preferences. Below are some images of a microbat that I saved from a tree during a thorough post-felling check before it was mulched. The bat underwent a health assessment and was released later that night. Please note that I am a trained and vaccinated Ecologist and Wildlife Carer, never touch a bat and leave it to the professionals.
As if land clearing isn’t bad enough, many bats would have also died during the large scale 2019-2020 bushfires that burnt more than 100,000 hectares. These impacts can be long-lasting and in combination with land clearing, detrimental. This has been especially true for the threatened (in NSW) golden-tipped bat (Phoniscus papuensis), which suffered a loss of 40% of its habitat in the NSW bushfires. As we undergo climate change, bushfires may become more frequent and severe, which could push ecosystems beyond recovery, causing a further decline of bat species, among many other species.
Promotion of bat richness
Maintaining and enhancing bat richness can be achieved by retaining natural tree structures and an understorey that has not been strongly modified by grazers or cropping. It is important that farmers maintain native vegetation to enhance foraging opportunities and roosting habitats to ensure the continuation of microbat communities within their farm.
Where native habitats are lacking or declining, a maintenance strategy to increase and/or sustain bat richness is tree retention, re-planting of native trees, not pruning dead branches from trees (as they provide critical roosting habitat) and installing roosting boxes which can provide bats a safe place to rest and sleep throughout winter. Other ways farmers can increase bat numbers are to lessen key threats, such as ceasing firewood collection and disturbance of habitat.
Simple ways both farmers and landholders can minimise threats to bats are feral dog and cat management, which includes keeping domestic pets inside (particularly at night), removal of Cocos Palms (for megabats, which are important pollinators in our ecosystem), and other invasive weeds. Implementing these simple solutions will result in a friendship that is mutually beneficial for both farmers and the environment.
To find out more about microbats visit: https://www.ausbats.org.au/bat-fact-sheets.html
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MacKinnon, L. (2007). Microbats in changing cotton production landscapes. The University of Sydney, Retrieved from: http://www.insidecotton.com/jspui/bitstream/1/3841/1/CRC57%20Thesis.pdf
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Michaels, F. (2021). Bats – Why we need them! Green Harvest, Retrieved from: https://greenharvest.com.au/PestControlOrganic/Information/Bat.html
NSW Landcare. (2021). Microbats on Farms Workshop. Young District Landcare, Retrieved from: https://landcare.nsw.gov.au/groups/young-district-landcare-inc/microbats-on-farms-workshop/
Queensland Government. (2019). Micro bats: The insect terminators. Retrieved from: https://environment.des.qld.gov.au/wildlife/animals/living-with/bats/micro-bats#living_with_micro_bats
Rozenbaum, M. (2019). Why do bats have such a bad reputation? Understanding Animal Research, Retrieved from: https://www.understandinganimalresearch.org.uk/news/communications-media/bats-bad-rap/
Upper Campaspe Landcare Network. (2021). Bats and pollination. QLD, Retrieved from: https://www.uppercampaspelandcare.org.au/bats-and-pollination/