Moose and lobsters have a few differences, don't they? The way we can trap them is equally as different. Trapping may seem like a bad thing but it is actually successfully integrated into ecological monitoring. Ecological monitoring is a vital part of managing protected areas. It counts hunted specimens when considering the density and health of a population.
It is risky to trap large animals such as moose for ecological purposes alone, and it is rarely done that way. We more often use camera "traps" instead, and "shoot" them with a (usually invisible) beam of infrared light. For lobsters, we go to boats that trawl sea floors, to examine them.
Trapping Meaning
Trapping in ecology is the process of capturing and confining a target animal for purposes such as:
Trapping is a centuries-old practice that has been used for both practical and traditional purposes. Today, it continues to play an important role in ecology, particularly in the management of wildlife populations. It is often used when animals need to be relocated due to human encroachment.
Trapping Laws
Trapping is a highly regulated activity in many jurisdictions, and strict laws govern the types of traps that can be used and the manner in which they can be deployed.
- In the UK, general wildlife trapping is regulated by the Humane Trapping Standards Regulations 2019, which was amended to the 1981 Wildlife and Countryside Act; as well as by the Conservation of Habitats and Species Regulations 2017.
- Licences for trapping or for the surveying and handling of bats, birds, small mammals, etc. are issued by the Department for Environment Food & Rural Affairs (DEFRA) for England, Natural Resources Wales (NRW) for Wales, NatureScot for Scotland, and the Department of Agriculture, Environment and Rural Affairs (DAERA) for Northern Ireland.1
When used responsibly, trapping can be an effective and humane tool for managing wildlife populations.
Trapping is part of the surveying methods used by ecologists. They follow the best practice guidelines imposed by each type (bird, mammal, insect, etc.) or species of animal.
Best practice guidelines are not legally enforceable like legislation is but are issued by Conservation Trusts or the professional membership bodies of a country.
For the UK, one of the leading bodies would be CIEEM - Chartered Institute of Ecology and Environmental Management, which professionals can apply to become members of.
Welfare standards may include the need to provide food, drink, and shelter inside the trap.
Trapping welfare standards in the UK are regulated by the Animal Welfare Act 2006 and its analogues in Northern Ireland and Scotland.
A trap can be either lethal or non-lethal, depending on its intended use.
Lethal trapping is used most often for insects, especially if not endangered, but much less for other species, unless they are considered pests or invasive species from an ecological perspective.
Traps and Statistical Analysis
The right kind of traps (based on species, size, location, etc.) need to be paired with the correct statistical analysis techniques.
A statistical analysis technique is a commonly used technique to examine data sets and look for patterns. This type of analysis can be used to study everything from population dynamics to predator-prey interactions.
There are a variety of different statistical methods that ecologists can use, and the choice of method often depends on the type of data that is being analysed.
The Lincoln Index is a simple averaging formula used for estimation purposes once part of a population had already been caught. It makes use of trapping and release in two stages. It sums up the number of individuals caught in the first stage with the number of individuals caught in the second stage. Then, it divides the resulting number by the number of individuals caught in the second stage that already had marks (from having previously been caught).
Mean standard deviation (adding data items and then dividing by the total number), regression analysis (can be used to examine the relationship between tree height and diameter), and hypothesis testing (can be used to test the hypothesis that tree height affects diameter) are all valid techniques that are used in conjuncture with trapping.
Complex multivariate analysis techniques, such as Kendall's W, may be required when different data needs to be superimposed (meaning laying data on top of each other for better visualization), such as for soil biodiversity analyses.
Kendall coefficient of concordance (Kendall's W) is a measure of how well individuals sorted into ranks correspond with one another. The coefficient ranges from -1 to 1, with 1 indicating perfect agreement and -1 indicating perfect disagreement. A value of 0 indicates random agreement. Kendall's coefficient is often used to compare different methods of ranking species according to their abundance. It can also be used to compare rankings of sites according to their suitability for a particular species.2
Best practice in animal trapping
It is especially important to exercise care when setting up and handling animal traps. Considerations and best practice measures include:
Minimal disturbance of the surrounding environment: reduced or no vegetation trampling, uprooting, loud noises, waste left behind, etc.
Environmental conditions recording: making sure that the conditions in which the trap is set, and the animal is caught are recorded: sunlight, wind speed, precipitations, etc.
Appropriate apparatus usage: making sure the specific instruments that help take quantitative measurements are functioning well, for example, pH meters, water turbidity meters, altimeters measuring altitude, handheld sonars for echolocation, etc.
Risk assessment: identify the risks surrounding the person setting or examining a trap, and the animal being trapped.
Let's look at what can happen to a trapped animal in general.
A trapped animal can become easy prey to another who can snatch it from the trap. Reasons for this include the inability to run away or fight (e.g. in case a limb is caught), panic, or exhaustion (muscle fatigue from trying to run away, the risk of self-mutilation).
Large-bodied crocodilians tend to use their snouts to break through a cage's walls or bite at it. This causes bruising. Lactic acid builds up rapidly in their muscles following struggle, which can lead to exhaustion and death.
Other animals, such as rabbits and deer, are similarly adapted to short bursts of struggle, rather than to prolonged stress. They are more likely to be weakened and preyed upon following a stressful trapping and capture incident.
Trapping Reasons
Reasons why trapping is necessary usually include the need to get or verify accurate wildlife data.
| Subject | Description |
| Animal population health | - The practical examination of an animal allows for weight, size, sex, or biological sample (e.g. blood) examination.
- Lineages can only be established by analysing genetic material from identified individuals.
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| Public health | - Animal population shifts and movements can be vectors for diseases or affect (positively or negatively) human activities.
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| Data accuracy | - Directly handling animals allows for the verification of satellite or indirect data.
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| Behavioural research | - Trapping means correct positioning, but also understanding what attracts (lures) and guides animals into a cage or trap, usually in the form of food or pheromones.
- Different lures or traps may be used to understand food preferences, spatial and object awareness, what time of the day an animal is most active, and seasonal occurrences.
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Information obtained from trapping (and trapping itself) can further be used to:
- Relocate wildlife
- Control population size
- Manage biotic or abiotic impacts on the environment
Placing of Traps
A quadrat of any shape, such as a circle, may be established, that can be as small as a few metres or as big as a few acres. Traps are placed within its perimeter. All caught animals this way are marked, until more marked ones are caught than unmarked ones.
If the animals are caught alive, but the researchers know the traps cannot be verified before the weather conditions are likely to change (the day-night cycle), the cages should be provided with thermoregulatory material, such as flax or cotton.
A thermoregulatory material refers to a textile that helps maintain cool when it is warm and body heat when it is cold.
Rodents such as dormice are sensitive to cold when left in a cage overnight.
Types of Traps
All traps have specific limitations regarding the size of organisms they can catch and how many they will at the same time. It is often difficult to accommodate more than one organism in the same trap, but the more social or tolerant a species is, the better the chances to accommodate more in the same trap.
Insect Traps
All the following types of traps, except for spring traps, can be successfully used on insects. "Falling traps" and nets, as described below, may be among the most popular insect traps.
Pitfall Trapping
This can be a container or a cavity, dug inside soil or other materials, with an opening at the top, which collect organisms that fall in.
Nature's own pitfall trap
"Pitfall trapping" has been achieved by evolution as well. Carnivorous plants, such as Bromeliads (flowering plants of the family Bromeliaceae), have modified their leaves to resemble cups and be slippery. They secrete juices that attract and digest unsuspicious insects that fall in. Sometimes, pitcher plants resort to digesting the droppings of wild animals such as bats, instead.
Tullgren Funnel
Tullgren funnel trapping is a method of trapping using a light source. It collects soil arthropods (members of the phylum Arthropoda, also known as insects) by exploiting their positive or negative response to light. A tullgren funnel consists of a glass funnel with a narrow inner neck, placed inside a larger container, such as a jar. The neck of the funnel is placed over a light bulb, which heats the air inside the funnel and causes the arthropods to move away from the light and fall into the container. Tullgren funnel traps can be used to collect a variety of small arthropods, including mites, springtails, and ants.3 This method is particularly useful for sampling soil invertebrates in the tundra and other areas where light is scarce.
Nets
Nets are a common tool used in wildlife trapping. They can be used to capture animals of all sizes, from small rodents to large mammals. Nets can be baited or unbaited, and they can be placed on the ground or suspended in the air. When an animal walks into or flies into a net, it becomes entangled and is unable to escape. Wildlife trappers often use nets to capture animals alive so that they can be relocated or studied.
Sensitive species, such as large birds, can risk injury to their wings when caught in nets, whereas underwater animals who need to breathe may be asphyxiated by nets which either restrict their movement and breathing or prevent them from resurfacing for oxygen.
Sweep nets, plankton nets (catching plankton-sized organisms), pond nets, or aerial nets (lightweight nets used to capture small flying organisms, especially insects) are easy tools to use for population capture and sampling, involving minimal risks to the organisms.
Pond nets can be used to collect small fish, crustaceans and invertebrates from riverbeds, shallow estuaries, etc.
Mammal Traps
Some mammalian traps are designed to catch one specific species. Harp traps are specialised in catching bats. A set of very thin, perpendicular strings directs bats during flight into a funnel-like bag from which they cannot get out until the daytime when the trap will next be checked.
Spring traps tend to be used to catch mammals. Some other names are rubber-jaw traps, or padded traps. They have rubber instead of sharp teeth around the metal foothold, in order to avoid penetrating the animal's skin, albeit still being able to restrict it. They are powered by a spring that is pressure-sensitive. Such traps may usually restrict the blood flow in the caught limb and cause numbness. An animal should not be left caught in one for more than a day, due to the risk of self-harm.
Reptile Traps
Reptile traps can sometimes be tricky to set up. Great-crested newt traps in the UK, for instance, should be checked at least once daily and between a small two-hours window in the morning coinciding with the reptiles' movement! Additionally, cages are a good choice for catching live small and medium-sized terrestrial vertebrates. Cages offer some of the better welfare options available, such as the possibility of placing food, water and thermal matting inside.
Traps are a great tool for population sampling, but they must be calibrated or placed in ways which avoid hurting sensitive species. Too much power, light, heat, or similar behind a mechanism can lead to the stress and death of the caught organism.
Trapping - Key takeaways
- Wildlife trapping needs to follow animal welfare and wildlife regulations, and the trapper needs to hold a licence.
- Best practice guidelines for animal trapping are issued by trusts and membership bodies and are often a welcomed supplementary.
- Statistical analysis techniques are paired with animal trapping to understand population trends.
- Types of traps include pitfall traps, light, nets, funnels, spring traps, cages, etc.
- Traps can be operated differently depending on how humane we want them to be, but there is always a risk of stress and injury to the caught animal that is unaware of what is happening.
References
- BASC, Trapping pest birds code of practice, 2022
- Pier Luigi Buttigieg et al., A guide to statistical analysis in microbial ecology: a community-focused, living review of multivariate data analyses, 2014
- Massey University, Berlese-Tullgren apparatus, 2021
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