Pitfall trap
Encyclopedia
A pitfall trap is a trapping pit
for small animals, such as insects, amphibians and reptiles. Pitfall traps are mainly used for ecology studies and ecologic pest control. Animals that enter a pitfall trap are unable to escape, and may either be killed by the trap or remain unharmed. This is a form of passive collection, as opposed to active collection where the collector catches each animal (by hand or with a device like a butterfly net
). Active collection may be difficult or time consuming, especially in habitats where it is hard to see the animals such as thick grass or leaf litter.
s that fall into it. Wet pitfall traps are basically the same, but contain a solution designed to kill and preserve the trapped animals. The fluids that can be used in these traps include formalin (10% formaldehyde), methylated spirits, alcohol, ethylene glycol
, trisodium phosphate, picric acid or even (with daily checked traps) plain water. A little detergent is usually added to break the surface tension
of the liquid to promote quick drowning.
The opening is usually covered by a sloped stone or lid or some other object. This is done to reduce the amount of rain and debris entering the trap, and to prevent animals in dry traps from drowning (when it rains) or overheating (during the day) as well as to keep out predators.
One or more fence-lines of some sort may be added to channel targets into the trap.
Traps may also be baited. Lures or baits of varying specificity can be used to increase the capture rate of a certain target species or group by placing them in, above or near the trap. Examples of baits include meat
, dung
, fruit
and pheromone
s.
s in which the trapping occurs. An animal's trappability depends on the structure of its habitat (e.g. density of vegetation, type of substrate). Gullan and Cranston (2005) recommend measuring and controlling for such variations. Intrinsic properties of the animal itself also affect its trappability: some taxa are more active than others (e.g. higher physiological activity or ranging over a wider area), more likely to avoid the trap, less likely to be found on the ground (e.g. tree-dwelling species that occasionally move across the terrain), or too large to be trapped (or large enough to escape if trapped). Trappability can also be affected by conditions such as temperature or rain, which may alter the animal's behaviour. The capture rate is therefore proportional not only to how abundant a given type of animal is (which is often the factor of interest), but how easily they are trapped. Comparisons between different groups must therefore take into account variation in habitat structure and complexity, changes in ecological conditions over time and the innate differences in species.
Trapping pit
Trapping pits are deep pits dug into the ground, or built from stone, in order to trap animals.European rock drawings and cave paintings reveal that the elk and moose have been hunted since the stone age using trapping pits. In Northern Scandinavia one can still find remains of trapping pits used...
for small animals, such as insects, amphibians and reptiles. Pitfall traps are mainly used for ecology studies and ecologic pest control. Animals that enter a pitfall trap are unable to escape, and may either be killed by the trap or remain unharmed. This is a form of passive collection, as opposed to active collection where the collector catches each animal (by hand or with a device like a butterfly net
Butterfly net
A butterfly net is one of several kinds of nets used to collect insects. The entire bag of the net is generally constructed from a lightweight mesh to minimize damage to delicate butterfly wings. Other types of nets used in insect collecting include beat nets, aquatic nets, and sweep nets....
). Active collection may be difficult or time consuming, especially in habitats where it is hard to see the animals such as thick grass or leaf litter.
Structure and composition
Pitfall traps come in a variety of sizes and designs. They come in 2 main forms: dry and wet pitfall traps. Dry pitfall traps consist of a container (tin, jar or drum) buried in the ground with its rim at surface level used to trap mobile animalAnimal
Animals are a major group of multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously and...
s that fall into it. Wet pitfall traps are basically the same, but contain a solution designed to kill and preserve the trapped animals. The fluids that can be used in these traps include formalin (10% formaldehyde), methylated spirits, alcohol, ethylene glycol
Ethylene glycol
Ethylene glycol is an organic compound widely used as an automotive antifreeze and a precursor to polymers. In its pure form, it is an odorless, colorless, syrupy, sweet-tasting liquid...
, trisodium phosphate, picric acid or even (with daily checked traps) plain water. A little detergent is usually added to break the surface tension
Surface tension
Surface tension is a property of the surface of a liquid that allows it to resist an external force. It is revealed, for example, in floating of some objects on the surface of water, even though they are denser than water, and in the ability of some insects to run on the water surface...
of the liquid to promote quick drowning.
The opening is usually covered by a sloped stone or lid or some other object. This is done to reduce the amount of rain and debris entering the trap, and to prevent animals in dry traps from drowning (when it rains) or overheating (during the day) as well as to keep out predators.
One or more fence-lines of some sort may be added to channel targets into the trap.
Traps may also be baited. Lures or baits of varying specificity can be used to increase the capture rate of a certain target species or group by placing them in, above or near the trap. Examples of baits include meat
Meat
Meat is animal flesh that is used as food. Most often, this means the skeletal muscle and associated fat and other tissues, but it may also describe other edible tissues such as organs and offal...
, dung
Feces
Feces, faeces, or fæces is a waste product from an animal's digestive tract expelled through the anus or cloaca during defecation.-Etymology:...
, fruit
Fruit
In broad terms, a fruit is a structure of a plant that contains its seeds.The term has different meanings dependent on context. In non-technical usage, such as food preparation, fruit normally means the fleshy seed-associated structures of certain plants that are sweet and edible in the raw state,...
and pheromone
Pheromone
A pheromone is a secreted or excreted chemical factor that triggers a social response in members of the same species. Pheromones are chemicals capable of acting outside the body of the secreting individual to impact the behavior of the receiving individual...
s.
Uses
Pitfall traps can be used for various purposes:- During the mating seasons of toads, frogs and salamanders in temperate climates, these animals often have to cross busy roads on their way from wintering grounds to breeding ponds. To prevent them from being killed, volunteers may place low fences along roads which the animals have to cross. On short distances dry pitfall traps are then placed along the fences to collect the animals, which subsequently are manually transferred to the other side of the road, thus preventing massive roadkill.
- Collectors and researchers of various ground-dwelling arthropodArthropodAn arthropod is an invertebrate animal having an exoskeleton , a segmented body, and jointed appendages. Arthropods are members of the phylum Arthropoda , and include the insects, arachnids, crustaceans, and others...
species may use pitfall traps to collect the animals they are interested in. This can be done without bait (for e.g. ground beetles and spiders) or with bait (for e.g. dung beetles). - When used in series, these traps may also be used to estimate species richnessSpecies richnessSpecies richness is the number of different species in a given area. It is represented in equation form as S.Species richness is the fundamental unit in which to assess the homogeneity of an environment. Typically, species richness is used in conservation studies to determine the sensitivity of...
(number of species present) and abundances (number of individuals), and this combined information may be used to calculate biodiversity indices (e.g. the Shannon indexShannon indexThe Shannon index, sometimes referred to as the Shannon-Wiener Index or the Shannon-Weaver Index, is one of several diversity indices used to measure diversity in categorical data. It is simply the Information entropy of the distribution, treating species as symbols and their relative population...
).
Some problems with pitfall trapping
There are inevitably biases in pitfall sampling when it comes to comparison of different groups of animals and different habitatHabitat
* Habitat , a place where a species lives and grows*Human habitat, a place where humans live, work or play** Space habitat, a space station intended as a permanent settlement...
s in which the trapping occurs. An animal's trappability depends on the structure of its habitat (e.g. density of vegetation, type of substrate). Gullan and Cranston (2005) recommend measuring and controlling for such variations. Intrinsic properties of the animal itself also affect its trappability: some taxa are more active than others (e.g. higher physiological activity or ranging over a wider area), more likely to avoid the trap, less likely to be found on the ground (e.g. tree-dwelling species that occasionally move across the terrain), or too large to be trapped (or large enough to escape if trapped). Trappability can also be affected by conditions such as temperature or rain, which may alter the animal's behaviour. The capture rate is therefore proportional not only to how abundant a given type of animal is (which is often the factor of interest), but how easily they are trapped. Comparisons between different groups must therefore take into account variation in habitat structure and complexity, changes in ecological conditions over time and the innate differences in species.
See also
- Insect collectingInsect collectingInsect collecting is the collection of insects for hobby, scientific study or profit. Historically insect collecting has been widespread and a very popular educational hobby. Insect collecting has left traces in European cultural history, literature and songs Insect collecting is the collection of...
- Malaise trapMalaise trapA Malaise trap is a large, tent-like structure used for trapping flying insects particularly Hymenoptera and Diptera. The trap is made of a material such as terylene netting and can be various colours. Insects fly into the tent wall and are funnelled into a collecting vessel attached to highest point...
- Flight Interception TrapFlight Interception TrapThe Flight Interception Trap or FIT is a widely used trapping system for flying insects. It is especially well-suited for collecting beetles, since these animals usually drop themselves after flying into an object, rather than flying upward...
(FIT) - Bottle trapBottle trapBottle trap is a name used for several different objects. Among these are a piece of material used in bathroom plumbing, as well as various traps that are made out of discarded bottles and which are used to trap animals as different as beetles, mice, fish and octopuses...