Connectivity of green and blue infrastructures: living veins for biodiverse and healthy cities

Data collection for BIOVEINS: Bees, bats, flowers and insects

Recently I caught up with the BIOVEINS teams from Paris and Zurich to find out what kind of data they have been collecting.

Nicolas Deguines and Romain Lorrillière, postdoctoral researchers working with Francois Chiron in the Ecology, Systematics and Evolution group at Université Paris-Sud have carried out several of the data collection procedures in Paris.

Last spring, the Zurich team came to Paris to install their bee hotels in 12 parks. However, at that time they didn’t have permission to do it. So François and Romain installed the hotels the following month. This involved climbing up ladders and attaching small wooden boxes full of tubes of straw with straps around the trunks of trees. The bee hotels full of straw provide nesting spaces for wild bees. Inside the straws, bees lay their eggs, which will turn into larvae inside the straws, and finally pupate to turn into adult bees. Recently, the Zurich team went back to collect the boxes again and bring the boxes with their straws full of bee larvae back in Switzerland. The species will be identified when the adult bees emerge. Parasitism on the larvae may occur—bee hotels are often heavily parasitized since there is a high concentration of bee larvae in one place, rather than scattered throughout the landscape – but this may bring insights into how interactions between hosts and parasites develop within urban environments.

The bats will be studied through the recordings of their calls made with the batloggers installed in specific boxes in the bee hotels, at the 12 sites in Paris, to which 11 additional Paris sites with batloggers were added. The batloggers collected data for 5 nights each in May, June and September. They record the calls of the bats. Bats have at least two kinds of calls—regular calls they use for spotting obstacles and that indicate that they are just passing by, or very rapid calls highly modulated in frequency that they use for detecting and hunting insects. Each species has slightly different calls. The batloggers’ range of detection of bat calls depends on the habitat structure, and on the calls, since higher-frequency calls propagate shorter distances. This data will allow Nicolas to identify the species of bats present, and whether they are hunting or not. However, the total number of bats is impossible to estimate. In one park, a batlogger’s memory was completely full after one night, which could have been from a single bat passing back and forth in front of it all night. The call identification is done in a semi-automatic way using a computer programme, and then Nicolas checks it afterwards. There are 23 species of bats in the Ile-de-France region around Paris (<>). They present a large variety of hunting techniques—one, the greater noctule bat (Nyctalus lasiopterus), even hunts small birds! Because bats all prey on other animals, mainly invertebrates in France, they are good indicators of any changes occurring in the rest of the food chain, like prey biomass reduction which are themselves correlate to diversity and health of plants in cities.

Around the bee hotels, within a radius of 100 m, Nicolas and a masters student (Emeline Klimczak) also identified all the flowering plants present, in order to count the number of species and the abundance of flowering plants. They repeated this at the end of April, the beginning of June, and the end of July. This data will give an estimation of the nectar resources available for the bees and other insects.

Finally, in the 12 parks in Paris the Swiss team also installed night traps for nocturnal insects. These consisted of a plastic bottle with one side cut open and a small light installed inside to attract the insects. They would then either fly upwards and get trapped in the top of the bottle, or fall down and drown in a small container of liquid. This data will be correlated with the bat activity data to see if bats hunt more where there are more nocturnal insects, as one might expect.

PhD student Joan Casanelles from the Zurich team told me that his research as part of Bioveins, which will include rearing and identifying the bees from the bee hotels, and integrating the biodiversity data from plants and insects, is “always a surprising experience.” Urban green areas can be very different than expected due to differences in management, which can create a large diversity of small habitats such as tree pits, vegetation strips along roads (verges), and managed meadows. He also told me that “Working in public crowded areas frequently involves interactions with people who are curious about the activities I do. Although sometimes the communication may be difficult, it is a good chance…to explain the importance of urban areas for conservation.”

Photos (c) Romain Lorrillière, Nicolas Deguines.

--Meredith Root-Bernstein