saddle grasshopper (Evibeger Diornos) It occurs in the Netherlands exclusively in the nature reserves of Veluwe and a small population outside it. Despite the protected status of the areas in Veluwe, there is still a downward trend in the size of this population. Some potential bottlenecks include food availability and egg deposition problems. These two potential problems will be investigated this year by Stichting Bargerveen in collaboration with County Gelderland and the central government real estate agency.
DNA Food Research
In order to identify potential problems with the food supply, it is important to identify the food sources that juvenile and adult locusts use. The population of the Netherlands is still large and settled in the Artillery Marksmanship (ASK, Oldebroek) in North Veluwe. The food placement in this area appears to be fine, which makes it a good place to start in determining the species’ diet. However, there are exceptional circumstances in ASK; The effects of heavy munitions provide for the replacement of the soil, its supply of chemical elements and sometimes large fires. So additional data is being collected at an infantry shooting camp (ISK, Harskamp) where the saddle grasshopper has shrunk, but a small core population remains. The nutritional needs of juveniles and females are expected to be higher than those of adult males due to growth and egg production respectively. So the study distinguished between adult and immature animals, as well as between the sexes. In June, the nymphs of the saddle grasshopper are collected and in September the adults are collected. Captured animals are individually placed in jars and taken away. After a day and a night in the jar, the stool produced during that period is collected. After that, the animals are returned to the place where they were captured. The stool will then be analyzed for the DNA in it so that the diet can be determined.
The importance of bare sandy soil
In addition to the importance of food availability, an open sandy bottom is regularly cited as an important quality aspect of the saddle grasshopper’s habitat. The significance of this will be experimentally verified in a two-part study. First of all, it was determined whether the animals prefer a particular type of soil and whether they are willing to lay eggs in non-favorite soils. Under controlled conditions, trays are provided with a substrate for laying eggs, water and food and two saddle grasshoppers. In different tanks, the animals were given a choice of bare and mulched soils and a combination of two soils. The number of eggs deposited on each of the available substrates was subsequently counted to assign egg deposition preference. When a saddlery grasshopper can choose between a sandy, free bed and one that has grown algae, it always chooses a bare one. But when the female has no choice, she deposits her eggs in a moss package as well. So, after one experiment, we still don’t know how important soil is. Therefore, in a second experiment, it was determined whether mulched soil was a less favorable environment for egg development. This is done by examining the development of eggs in bare, sandy soils under field conditions. For this purpose, a layer of sand is placed on a number of sieves. Half of the sieves are covered with a top layer of bare sand. The rest is covered with a top layer covered with algae. Sieves with eggs are buried in open ground in the habitat of the saddle grasshopper. Before the normal egg development time (2 years), the sieves are dug up and the eggs stored at 20°C to allow them to grow. The number of nymphs that hatch from the eggs is counted to determine the reproductive success of the different bottoms. For now, we eat rusks with mice every day, because the young grasshoppers are busy leaving the nursery.
Expectations and results
These Bargerveen studies will provide more information about the potential problems of the saddle grasshopper with the food supply and spawning. As a result, this species can be taken into account in land use and management and current numbers can be maintained.
Text: Kevin Gorts, Bargervin Foundation
Photos: Maren Njsen; Book Ten Kit; Jan Cooper