Skip to content

Conservation

Why did the dragonfly cross the road?

by Mario Balzan 07 Apr 2011
Why did the dragonfly cross the road?

''Crossing the road is an endeavour to which almost everyone who walks to anywhere at all will have to undertake at some point or another'', states the online BBC idiot's guide to crossing the road. The same applies for animals which are able to disperse and to utilise different habitat patches within the environment.

Several studies have suggested that roadways may represent barriers to this movement, and could act as sources of enhanced mortality, eventually eliminating these species from nearby habitats. Although it is a common observation that vast number of insects die on the grills and windshields of motor vehicles, few studies have actually attempted to quantify mortality rates, and similar research has mainly been directed at vertebrates. In a study, currently in press in Biological Conservation, researchers in the U.S. estimated the mortality rates and the influence of roads on dragonflies behaviour, in four roadways at the Des Plaines River Valley in Illinois. During this study, the researchers scanned the road for dead dragonflies and observed their behaviour along roadways

Dragonflies are one of the most ancient and beautiful orders of insects. They are frequently top predators in wetlands, especially when fish are not present, and the predaceous younger larval stages are entirely confined to water habitats. The adults are mobile and are able to move around in order to accommodate for the various terrestrial ecological needs.

Similar to vertebrates, dragonflies have relatively low population size and s long-lived adult lifespan, and are therefore more susceptible to various threats including direct roadway mortality. In the United States, 277 of the 441 dragonfly species are considered of great conservation need in at least part of their range, and about 8.5% of these are listed as threatened or endangered in the International Union for Conservation of Nature (IUCN) redlist. Globally, threats to dragonflies include water use, pollution (example from agricultural chemicals), habitat degradation and loss, as well as the introduction of alien species, such as predatory fish.

Results obtained from the study carried out in Illinois provided no evidence that roads act as barriers to dragonfly movement. Indeed, most of the adult dragonflies recorded in flight actually crossed to the other side of the road, but were less likely to undertake the endeavour for roads characterised with the highest volume of traffic. However, large numbers of dead dragonflies were collected over the flight season, suggesting that motor vehicle collisions directly impact on populations of dragonflies through roadway mortality.

The study also demonstrates that some species are more susceptible to direct mortality, with two species in particular making more than 70% of the collected dead dragonflies. This was explained by the comparatively low height flights (typically under 2m) and relative lack of agility of these species. The impacts of roadways on dragonflies are complex and intrinsically linked to their ecology. Nevertheless, this study demonstrates the need to assess the biological long-term impacts of roadways and the importance of considering not only larger fauna, but also normally overlooked taxa, when planning the location of new roads.


Trending Eco-Friendly Clothing

Love My Planet Women's Relaxed Fit Hoodie
Earth
Quick Add
Close
Notify me
Notify me
Love My Planet Women's Relaxed Fit Hoodie
Love My Planet women's eco-friendly relaxed fit hoodieSize Guide Centimeters 8 10 12 14 16 18 Bust 84 88 92 97 103 108 Waist 66 70 75 80 85 91 Hips 91 95 99 104 109 116 Bust: Measure around the fullest part of...
£38.00
£38.00
Close
Notify me
Notify me
Penguins Hate Push-Ups Men's Pullover Hoodie
Earth
Quick Add
Close
Notify me
Notify me
Penguins Hate Push-Ups Men's Pullover Hoodie
Penguins Hate Push-Ups men's eco-friendly pullover HoodieSize Guide Centimeters XS S M L XL XXL Height 171 175 179 183 189 195 Chest 86 93 99 104 116 129 Waist 71 76 81 89 99 112 Chest: Measure all round your chest just below...
£38.00
£38.00
Close
Notify me
Notify me
Lightning Bolt Kids Long Sleeve T-Shirt
Earth
Quick Add
Close
Notify me
Notify me
Notify me
Lightning Bolt Kids Long Sleeve T-Shirt
Lightning Bolt kids eco-friendly long sleeve t-shirtSize Guide Centimeters 3-4yrs 5-6yrs 7-8yrs 9-10yrs 11-12yrs Height 98 112 125 136 147 Chest 60 66 70 75 84 Chest: Measure all around your chest just below your armpits. Height: Your natural height If you fall between...
£18.00
£18.00
Close
Notify me
Notify me
Notify me
Union Jack Tote Bag
Earth
Quick Add
Close
Notify me
Notify me
Union Jack Tote Bag
Union Jack eco-friendly colour tote bagProduct Specification Organic Cotton Tote Bag. Twill Weave (170gsm). 37 x 42 cm (7cm gusset.) Made in India / Designed on the Isle of Wight. Wash Cool, Hang Dry.
£16.00
£16.00
Close
Notify me
Notify me
Prev Post
Next Post

Eco-Friendly Shop

Women's Clothing

Eco-Friendly Clothing for Women Our online shop offers a wide range of sustainable women’s clothing products, including t-shirts, hoodies, vests, sweaters, shorts, and...
Shop Now

Men's Clothing

Eco-Friendly Clothing for Men Our online shop offers a wide range of sustainable men’s clothing products, including t-shirts, hoodies, vests, sweaters, shorts, and...
Shop Now

Kids Clothing

Eco-Friendly Clothes for Kids Our online shop offers a wide range of sustainable kids clothing products, including t-shirts, hoodies and jumpers. Our garments...
Shop Now
Someone recently bought a
[time] ago, from [location]

Thanks for subscribing!

This email has been registered!

Shop the look

Choose Options

Earth Times
Sign up for exclusive updates, new arrivals & insider only discounts

Recently Viewed

Edit Option
Back In Stock Notification
this is just a warning
Login
Shopping Cart
0 items

Before you leave...

Take 20% off your first order

20% off

Enter the code below at checkout to get 20% off your first order

CODESALE20

Continue Shopping