Nature and Agriculture
The Impact of Mowing on Wildlife and why we Must Save Fawns From Being Killed by Mowers
The Mowing
Farmers mow the meadows repeatedly between May and October to obtain feed for their livestock. The mown grass is either fed fresh, ensiled or dried to make hay. Silage and hay are durable and can therefore be fed all year round. Rotary mowers mounted on tractors are generally used for mowing. Up to three mowers can be attached to the rear and/or front of the tractor, achieving working widths of between 2 m and 15 m. Depending on the height of the grass, which can be between approx. 20 cm and 1 metre, mowing is carried out at speeds of up to 20 km/h. Depending on weather-related growth, the grass is ready for the first cut between mid-May and early June and is then usually 60 cm to 1 m high.
Hidden Fawns
Deer originally inhabited forest edges and clearings, but have now adapted to almost treeless agricultural steppes. They give birth to their young, fawns, in May and June, timing this to coincide with the weather-dependent growth of grass. Tall grass provides abundant food for the mother deer, the doe, as well as the necessary hiding place for the fawns. For the first 10 to 14 days of their lives, the fawns do not accompany the doe, but lie alone in the tall grass on the meadow floor. The doe stays nearby, visiting the fawn at its resting place about every four hours to suckle it and then leaving again. The fawns are hidden and protected from their natural enemies, foxes, wolves and golden eagles, in the tall grass. This is aided by their camouflaged spotted coat, their lack of body odour in the first days of life and their lack of flight instinct. As escape in tall grass would be futile for the small animals, they ‘press themselves down’ when disturbed, i.e. they remain motionless and their natural enemies do not notice them. This protective strategy fails when the meadow is mowed with rotary mowers. It is almost impossible for the tractor driver to spot a fawn’s hiding place while working. Even for a person searching the meadow on foot, it is very difficult and time-consuming to spot a fawn in tall grass.
The Silage
Silage conversion transforms grass into silage and preserves it. To do this, it must be dried after mowing and then sealed in an airtight container. Anaerobic bacteria present in the grass then ferment the sugar in the grass, producing lactic acid, among other things, which has a preservative effect at a pH value of 4 to 4.5. The picture shows silage bales; the cut grass is wrapped in many layers of plastic film by machine and thus portioned. The film ensures the necessary airtight seal and also provides weatherproof and robust storage and transport packaging.
Among the many types of bacteria found in nature is the Clostridium botulinum group, which occurs as spores in dust and soil. The spores develop into bacteria in the absence of air on animal protein. They multiply and metabolise the protein, producing toxins from the botulinum toxin group. Even in very small quantities, this odourless nerve toxin is lethal to humans and many vertebrates. If parts of fawn carcasses or similar are present in the silage bales, Clostridium botulinum can develop there. If cows or horses are fed the silage, they may die in the worst case. There have been cases of poisoning from this cause in which ten or more cattle died from just one contaminated feed ration. A fawn killed during mowing can therefore cause great economic damage.
Wildlife Rescue Strategies
Even though the focus here is on saving fawns, it is useful to take a comprehensive look at the issue of meadow mowing. In addition to fawns, young hares and, above all, ground-nesting birds (pheasants, partridges, lapwings, curlews, larks and many other songbirds) and their broods are also at risk. There are many ways to protect wild animals from being killed by mowers. Each of these methods is better than doing nothing at all. The species and its behaviour play a decisive role in the success of the measure. In principle, all approaches to wildlife rescue can be divided into the following three categories: deter, drive away, find and take into custody, and exclude the meadow or meadow areas from mowing.
Mowing Strategy
From a wildlife rescue perspective, this is the cheapest and simplest method. For farmers, however, it is not the most profitable way to harvest feed.
Scarecrows
Scarecrows are suitable for protecting animals that are capable of fleeing from being killed by mowers.
Search and Rescue
This strategy is more reliable, but usually also more costly. The area to be mowed is searched thoroughly. Any animals found are carried away or confined on site.
Mowing Strategy
The most effective protection is choosing the right time to mow. Approximately 96% of fawns are born in May and June. If the first cut takes place in April and the second cut is delayed until late July, many fawns will be spared.
The type of mower also has an impact on the number of casualties. Today, there are mowers with a working width of 14 metres and working speeds of up to 24 kilometres per hour. Sometimes, even adult deer cannot escape them in time. In contrast to scythes and rotary mowers, cutter bars have been shown in numerous studies to be the most fauna-friendly mowing option. Many smaller animals – including hares – are spared if the cutting height is at least 12 cm. The two patterns shown in the illustration opposite are recommended so that animals that are able to flee have a chance to do so. However, this does not help fawns in the first days of life.
Scarecrows
In Sweden, a study was conducted in 1998 and 1999 on the effectiveness of plastic rubbish bags used as scarecrows on wooden stakes. According to the author, the correct use of scarecrows results in significantly more fawns being led away from the meadow than without scarecrows. In the experiment, the does removed 18 of 22 fawns from the danger zone on the first day after the scarecrows were set up. Setting them up too early causes the fawns to become accustomed to the scarecrows. However, if the scarecrows are set up too late, the does may not have enough time to bring their fawns to safety. Therefore, the scarecrows should be set up 1–2 days before mowing. In addition to simple plastic bags, there are a number of commercially available scarecrows that emit visual, acoustic or olfactory stimuli to scare the animals away. The illustration opposite shows various scarecrows. According to several manufacturers, the range of a visual/acoustic scare device is approximately 100 m. The olfactory scare device has a range of 10–20 m. Some hunters swear by the use of their hunting dogs to spread their scent. By running through the meadow with their dogs, the dogs’ scent is distributed throughout the field, which is supposed to have a similar effect to the scare devices mentioned above. Mowing an area the evening before mowing also has a similar scare effect. Recently, various acoustic wildlife deterrents with a noise level of up to 120 dB have been frequently advertised, which can be mounted on the mower. However, fawns younger than 3 weeks cannot be scared away with these. There are also protective devices for mowers that comb through the area in front of the mower like a comb. Fawns that are approximately 3–5 weeks old are startled when they are touched by such a device.
Search and Rescue
Dogs can find fawns despite their weak scent with their noses. Such pointing dogs can be trained in special dog schools. Searching with them is often more successful than with human chains, as shown in the picture opposite. In some places, entire school classes are hired to walk through the meadows on foot to find the fawns hidden there.
One system that has proven itself over many years is the infrared wildlife detector, which is sold by ISA Industrieelektronik. It consists of a 5-metre-long pole equipped with infrared sensors. You hang this pole around your neck and carry it through the meadow, as shown in the picture. If there is something warm lying in the meadow, the device beeps.
However, the greatest area coverage is achieved with a drone equipped with a thermal imaging camera. This can cover an area of approximately 20 hectares per hour.
Animal mowed
If a fawn gets caught in a mower, it is usually killed. In many cases, it survives with serious or minor injuries. In this case, the responsible hunting leaseholder should be informed immediately, as they are authorised to decide on how to proceed. If the animal has minor injuries, it can be released after mowing, with or without treatment. In individual cases, fawns that have lost a leg, for example, can be raised by humans. The three-legged deer cannot be released into the wild later on, but remains in human care for the rest of its life. In the case of more serious injuries, the fawn must be killed.
However, death by mowing can also have further consequences. In the worst case, the perpetrator can face a prison sentence of up to three years. See legal situation.
In addition, farmers may suffer economic losses if parts of carcasses remain in freshly cut grass.