Monitoring Beetles: Effective Population Size Strategies

Monitoring beetle populations is important for conservation efforts, as beetles are the most diverse order of insects, making up about 40% of all insect species. Beetles are found in almost every habitat except the sea and polar regions, and they play a crucial role in ecosystems by feeding on plants and fungi, breaking down animal and plant debris, and eating other invertebrates.

To monitor beetle populations, scientists employ various methods, including mark-recapture studies and citizen science initiatives. Mark-recapture studies involve capturing and marking individual beetles before releasing them and then recapturing them at a later date to estimate population size. Citizen science projects, on the other hand, rely on volunteers to help monitor beetle populations and habitats.

Additionally, new technologies such as photographic mark-recapture (PMR) techniques are being explored as a cost-effective and minimally invasive way to study population dynamics. PMR uses digital photography and image analysis tools to identify individual beetles based on their unique markings or colour patterns.

The choice of monitoring method depends on the species, habitat, and research objectives. Effective monitoring is crucial for understanding beetle population dynamics and implementing conservation measures to protect these fascinating insects.

Using citizen science to monitor population size, distribution and trends

Citizen science is a powerful tool for monitoring beetle population size, distribution, and trends. Citizen scientists can help collect data on the existence and health of beetle populations in their habitats. This is especially important given the threats to beetle populations and the need for conservation efforts.

Citizen science projects can be a cheap and efficient way to survey extensive territories and help address the lack of human power and funding for extensive surveys. They can mobilize a high number of volunteers and cover large geographic areas, thus greatly exceeding the efforts of a limited number of researchers.

However, citizen science projects also have some drawbacks, including the lack of taxonomic expertise, which can result in unreliable identifications, and a potential bias towards urban and suburban habitats. There are also costs associated with coordination, including keeping regular feedback and maintaining volunteer motivation.

To address these challenges, it is important to combine citizen science with other data sources, such as museum collections and entomological literature. This can help fill in gaps in knowledge and provide a more comprehensive understanding of beetle distribution and trends.

Overall, citizen science can be a valuable tool for monitoring beetle population size, distribution, and trends, but it should be used in conjunction with other data sources and carefully planned and coordinated to ensure accurate and reliable results.

Monitoring population size through photographic mark-recapture

Photographic mark-recapture (PMR) is a cost-effective, non-invasive way to study population sizes. It is especially useful for species with distinct markings or colour patterns. PMR is also less invasive than traditional capture-based marking methods, which can be costly, time-consuming, and affect the growth, survival, and behaviour of wildlife.

PMR involves photographing individuals that are either free-ranging or live-captured, using remotely triggered or handheld cameras. The photographs are then analysed using computer software, which identifies and matches the unique markings on the individuals. This process is known as image manipulation and pattern matching.

PMR has been used to study the population sizes of various species, including beetles, giraffes, seals, and salamanders. For example, a study on burying beetles used PMR to identify individual beetles based on the spot patterns on their elytra (hard wing covers). Another study used PMR to estimate the population size of the endangered Saimaa ringed seal by capturing photographs of their unique pelage patterns during the annual moulting season.

PMR can be a useful tool for monitoring population sizes, especially for endangered species. It is less dependent on varying winter conditions and can be carried out without disturbing the individuals. However, it is important to ensure that the markings used for identification are permanent and do not wash off or change over time.

Assessing the red list status (extinction risk) based on population monitoring data

Assessing the red list status (extinction risk) of the European stag beetle, for instance, requires the help of citizen scientists to monitor the population and habitat at many individual sites. The IUCN Red List of Threatened Species is the world's most comprehensive information source on the extinction risk of animals, fungi, and plants. Assessors place species into one of the IUCN Red List Categories, which indicate how close a species is to becoming extinct, based on a series of assessment criteria.

The IUCN Red List provides information about a species' range, population size, habitat and ecology, use and/or trade, threats, and conservation actions. The number of species assessed for the Red List has been increasing over time. As of 2023, of 150,388 species surveyed, 42,108 are considered at risk of extinction because of human activity, particularly overfishing, hunting, and land development.

The Red List is updated a few times per year, and it is used by a variety of people, governments, and organizations. The data is used to support and plan conservation actions and priorities, better understand environmental impact, and inform educators, students, and scientists.

The Red List Categories are:

• Extinct (EX)
• Extinct in the Wild (EW)
• Critically Endangered (CR)
• Endangered (EN)
• Vulnerable (VU)
• Near Threatened (NT)
• Lower Risk (LR)

The IUCN aims to have the category of every species re-evaluated at least every ten years, and every five years if possible. This is done in a peer-reviewed manner through IUCN Species Survival Commission Specialist Groups (SSC).

Population trend estimates used by Red List assessments should be as quantitative, comprehensive, and transparent as possible. The International Union for the Conservation of Nature (IUCN) considers population trends during Red List assessments (Criterion A). Given that the Red List is often used to determine conservation priorities, it is important that Red List assessors have the best available information regarding population trends of focal species.

Composite indices of population trends can aid Red List assessments by formally and quantitatively combining multiple lines of evidence from disparate monitoring programs into a single estimate. Such indices allow for simplified inference where the single estimate is easier to interpret than multiple unrelated datasets.

Raising awareness about the threats to the beetle population

Beetles are incredibly diverse, with more than 340,000 species worldwide, including nearly 30,000 in North America alone. They are important for the ecosystem, acting as predators of crop pests, keeping ecosystems clean as dung beetles and carrion feeders, and acting as pollinators in the tropics. However, despite their abundance and importance, beetles face many threats, and their populations are declining.

To raise awareness about the threats to the beetle population, it is essential to first understand the factors contributing to their decline. Here are some key messages that can be communicated to the public to achieve this:

• The Diversity and Importance of Beetles: Emphasize the incredible diversity of beetles, with thousands of species globally, and their vital ecological roles, such as pest control, waste management, and pollination. This will help people understand the significance of beetles in our ecosystems and why their conservation is crucial.
• Habitat Loss and Fragmentation: Explain how human activities, such as deforestation and urban development, are destroying and fragmenting beetle habitats, making it difficult for them to find food and suitable places to live and reproduce.
• Pesticide Use: Pesticides are designed to kill insects, and beetles are often unintentional victims. Communicate how the widespread use of pesticides in agriculture and residential areas is harmful to beetles and disrupts the natural balance of ecosystems.
• Climate Change: Climate change is a significant threat to many species, including beetles. Explain how changing temperatures, rainfall patterns, and extreme weather events are affecting beetle habitats and food sources, and how these changes can have cascading effects on the entire ecosystem.
• Light Pollution: While it may not seem obvious, light pollution can disrupt the natural behaviors of beetles, such as navigation and reproduction. Raise awareness about the impacts of artificial lighting on beetle populations and promote the use of beetle-friendly lighting fixtures.
• Disease: Diseases and parasites can decimate beetle populations, and with climate change, the risk of disease outbreaks increases. Share information about the potential impacts of diseases on beetles and the importance of early detection and management to prevent their spread.
• The Impact of Losing Beetles: Help people understand the consequences of beetle decline. For example, the loss of dung beetles and carrion feeders can lead to an increase in waste and a higher risk of disease transmission. Emphasize the interconnectedness of species and how the loss of beetles can have far-reaching effects on other organisms, including humans.

By communicating these key messages through various platforms, such as social media campaigns, educational programs, community outreach initiatives, and collaboration with conservation organizations, we can raise awareness about the threats to the beetle population and garner support for conservation efforts.

Using transects to monitor population size

Transects are an important method for monitoring beetle populations. Transects are used to monitor the European stag beetle, Lucanus cervus, in Poland, and the American burying beetle, Nicrophorus americanus, in the United States.

Transects are a type of fieldwork that involves setting up a line of traps to capture beetles. The traps are placed at regular intervals along a path, and the beetles are then counted and studied. This method can help determine the population size, distribution, and trends of beetle species.

In Poland, researchers set up transects in forested areas to study the distribution and habitat preferences of the European stag beetle. They found that the beetles were most commonly found in deciduous mesic forest sites and deciduous mixed mesic forest sites. The age of the trees colonised by stag beetles ranged from 70 to 248 years, with an average of 134 years.

In the United States, the American burying beetle recovery program has been using transects to monitor the beetle population on Block Island since the early 1990s. Field crews use pitfall traps to count the beetles, and they typically estimate between 750 to 1,000 beetles each year. This information helps them manage and support the beetle population.

Transects are an effective way to monitor beetle populations and can provide valuable data for conservation efforts. By studying the distribution and habitat preferences of beetles, we can better understand their ecology and develop strategies to protect them.

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