Every year, in the first weeks of May, a conflict between nature and agriculture occurs again with sometimes dramatic consequences for both sides.
The fawn rescue, or rather the problem that arises from the clash between nature and agriculture, comes back every year with the first grass harvest. The birth time of the fawn in late spring is also the time of the first grass cut in agriculture. Huge machines drive with meter-wide mowers over the harvest areas overgrown with tall grass. This is where the conflict between agriculture and nature arises. The lack of escape behaviour can quickly be fatal for the fawns.The manual fawn search or rescue, in which the harvest helpers scan the area before using the harvesting machines, is inefficient and prone to errors. Effective fawn rescue is different.
The deer mother gives birth to her fawn after 41 weeks of pregnancy. This happens between mid-May and mid-June. Normally a doe puts one or two fawns with a birth weight of about 1.5 kg. Fawns can already stand and walk a few minutes after birth. The doe feeds her fawns for about 2 months with milk. During the first weeks of life the fawns spend most of the time separated from their mother. In a curled-up prone position, it hides itself lying on the ground in the dense grass. The mother remains in the nearer surroundings of the fawn. Several times a day the fawns are fed by the doe. The fawns express the desire for their mother with quiet peeps.
Fawns have almost no own smell in the first weeks of life. The brownish fur with the white spots camouflages them very well in the grass and in the woods. These circumstances are the best protection against predators, but at the same time they make finding and rescuing fawns more difficult. In case of imminent danger, young fawns do not show any escape behaviour - they stay crouched on the ground in order not to be seen. Only at the greatest danger do fawns react with shrill, widely audible fielaps and thus alert their mother.
A only a few days old fawn typically remains effectively hidden in the grass, not visible for predators as also for the driver of a grass mower until it is too late. The fawn gets into the mower and is severely injured or killed. The so-called mowing of a fawn often even goes unnoticed. Meanwhile, in Germany it is a legal requirement that suitable, preventive fawn search and rescue actions must be taken to protect the fawns from being mowed.
Every year in Germany several hundred fawns are killed by mowing machines. There are even reports of several thousand fawns on the Internet. Every animal killed in this way is an unnecessary victim. It has not gone unnoticed that agriculture is under enormous time pressure, especially during harvest time.
The usual method with harvest helpers, who search the area for roe deer fawns before the mowers, is inefficient and is also not used everywhere. A much more suitable, because more efficient method for locating the fawns, which are often hidden in tall grass or grain, is the search by means of an Unmanned Aerial System (UAS), also known as a drone.
In the method of fawn search by UAS, the terrain is scanned from above with an infrared camera attached to the drone from the air. The terrain is scanned just right before the mowing process. After the rescue of the fawns, the entire searched area is secured in such a way that the doe cannot set down their fawns unnoticed in the same area again. Found fawns that have been rescued before the mowing unit are placed in boxes or correspondingly large cartons at the edge of the meadow and released again after the mowing process.
As the terrain can warm up during the course of the day due to sunlight, the early morning is the best time for a fawn rescue. At this time the ambient temperatures are still relatively low and the finding rate is high, as the temperature difference between the environment and the fawn is still large.
From the infrared aerial photographs taken by the UAS and the associated geo-coordinates, a presumed fawn position is transmitted to a GNSS handheld device in the form of GPS coordinates. One or more helpers equipped with such a GNSS handheld or mobile phone can then use the transmitted GPS coordinates to directly approach and inspect the potential find site.
If a fawn is found, it will be stored in a box secured to the edge of the meadow for the duration of the harvesting process and then returned to the edge of the meadow when the harvesting process is complete. This way the doe can find it again.
- Data acquisition: Thermal images/video are taken from the air using UAS
- Data evaluation: The potential fawn is recognized as such by the system
- Location: The position of the fawn is determined by means of the superordinate coordinates
- Position transmission: The data of the fawn's position is transmitted to a GNSS handheld device
- Rescue: The fawn can be manually removed from the area, and thus rescued