Pig traps

As pig traps aquatic fishing gear to be used (are traps ) indicates that especially for the detection of amphibians under feldherpetologischer studies (mapping) are used. After many attempts and presented prototypes, a trap type has prevailed that works on the principle of a swimming trap, so that it is ensured that there is enough space to breathe in the upper part of the trap chamber. When using pig traps, it is largely possible to dispense with the shearing off of bodies of water, which is usually associated with a serious disturbance of the submerged vegetation.

function

The most widespread fish trap based on the HENF design , the function of which is described here as an example, consists of a self-supporting plastic mesh cage to which two floats ( pontoons ) are attached. The pontoons are mounted in such a way that the upper area of the trap always protrudes from the water. This ensures that trapped lung breathers (e.g. newts ) can reach the surface of the water to breathe. With the trap shown here, due to its dimensions (30 × 30 × 50 cm), it is possible to sample both deeper (> 50 cm) and shallower (around 30 cm) bodies of water.

Pig traps work like "motion detectors" in the water. Depending on the water temperature, amphibians develop movement activities of different sizes. The warmer the water, the more active amphibians are; the more often they have to go to the surface of the water to breathe because of the increased metabolism . In doing so, they stumble upon the trap cage. In the case of fish traps made of lattice material, the pigs hold onto the lattice mesh and wander around the outside of the cage. Some of them find their way into the interior of the trap by chance via the trap funnel and are caught. The fact that newts swim to the surface of the water to emerge is made use of so-called emergence traps. Emerging traps have an (additional) trap entrance on the underside.

Attempts with “light baiting” have not led to significantly higher catch rates. However, an increase in the quota was observed for fish. The catchability of pig traps depends on the blocking effect and the funnel construction. Large traps with large funnel openings are more attractive than small traps, even if the funnel opening takes up the entire diameter of the trap.

Some authors warn against fish traps that are used completely submerged to capture amphibians. There is also a warning against the use of bottle traps, as this can lead to massive deaths of newts.

Catch spectrum

In addition to the actual target species group, the newts and their larvae, other aquatic organisms are also regularly caught. This includes all types of anurans ( Anura ), grass snakes ( Narix natrix ), dragonfly larvae , diving beetles and their larvae, corixidae , (small) fish etc.

The Dutch University of Utrecht used pig traps for the detection of mud whiskers ( Misgurnus fossilis ).

Comparative research

Some comparative studies on the catchability and functionality of pig traps or converted fish traps are available. M. Krappe reports on a field test in Mecklenburg-Western Pomerania, in the course of which two commercially available fish trap types were examined and the fish trap specially designed for catching newts had advantages in terms of catchability.

Legal basis

In Germany there are strict legal limits to the targeted use of pig traps. Since the target group of amphibians is "specially protected" or "strictly protected" species according to BNatSchG and BArtSchV, an exemption from the responsible nature conservation authority must be obtained before using newch traps.

Web links

Recommendations on the use of water traps for amphibian detection. - In: Kronshage, A. & Glandt, D. (2014): Water traps for amphibians - practical application in species protection (Researchgate) (with many pictures)

Individual evidence

↑ Susanne Meyer: Investigation of the survival strategy of the crested newt populations (Triturus cristatus, LAURENTI 1768) in the cultural landscape of Saxony-Anhalt - dissertation to obtain the academic degree Doctor rerum naturalium (Dr. rer. Nat.). Martin Luther University Halle-Wittenberg , 2005, 133 pp.
↑ Birgit Blosat: Experiences with self-made bottle traps , mailing 15/2009 from May 13, 2009.
↑ Martin Krappe: Methodical experiences with the amphibian mapping in Mecklenburg-Western Pomerania with special consideration of the use of two commercially available types of fish trap. - RANA 12 reports for field herpetology and ichthyofaunistics, 2011, 4–12.

[1] Susanne Meyer: Investigation of the survival strategy of the crested newt populations (Triturus cristatus, LAURENTI 1768) in the cultural landscape of Saxony-Anhalt - dissertation to obtain the academic degree Doctor rerum naturalium (Dr. rer. Nat.). Martin Luther University Halle-Wittenberg , 2005, 133 pp.

[2] Birgit Blosat: Experiences with self-made bottle traps , mailing 15/2009 from May 13, 2009.

[3] Martin Krappe: Methodical experiences with the amphibian mapping in Mecklenburg-Western Pomerania with special consideration of the use of two commercially available types of fish trap. - RANA 12 reports for field herpetology and ichthyofaunistics, 2011, 4–12.