Behavioral responses to mammalian grazing expose insect herbivores to elevated risk of avian predation
Abstract
Large mammalian herbivores (LMH) are important functional components and drivers of biodiversity and ecosystem functioning in grasslands. Yet their role in regulating food web dynamics and trophic cascades remains poorly understood. In the temperate grasslands of northern China, we explored whether and how grazing domestic cattle (Bos taurus) alter the predator-prey interactions between a dominant grasshopper (Euchorthippus unicolor) and its avian predator the Barn swallow (Hirundo rustica). Using two large manipulative field experiments we found that in the presence of cattle, grasshoppers increased their jumping frequency threefold, swallows increased their foraging visits to these fields six-fold, and grasshopper density was reduced by about 50%. By manipulatively controlling the grasshopper ability to jump, we showed that jumping enables grasshoppers to avoid being incidentally consumed or trampled by cattle. However, it increased their consumption rates by swallows 37 folds compared to grasshoppers that were unable to jump. Our findings illustrate how LMH can indirectly alter predator-prey interactions by affecting behavior of avian predators and herbivorous insects. The non-plant mediated effects of LMH on plant-dwelling arthropods in grazing ecosystems appears strong and common. We highlight that convoluted multispecies interactions may better explain how LMH control food-web dynamics in grasslands.
we explored the three trophic interactions between cattle (Bos taurus), grasshopper (Euchorthippus unicolor) prey, and Barn swallow (Hirundo rustica) predators in a temperate grassland in northeast China.
We first conducted a grazing experiment in the field to test the effects of livestock grazing on the jumping behavior and abundance of grasshoppers, and the visiting rate of swallows. We then manipulated the grasshopper ability to jump and tested whether the change in jumping behavior reduces the grasshopper probability to be killed by cattle, and increases their vulnerability to swallow predation.
Description of the Data and file structure (column and explanation)
Here is a guide to each tab:
Tab: grazing_experiment
Column Explanation
Year： Year of data collection in 2021
Block： Experimental block within which grazing treatments were embedded
Treatment： Grazing treatments
Ungrazed: cattle excluded
Grazed: cattle grazed
swallow_visits： Number of flying swallow visits in each plot (no./plot)
jumping_grasshopper： Number of jumping grasshoppers in two permanent quadrats in each plot (no./plot)
grasshopper_density： Grasshopper density (no./m2)
walkingsteps_cattle： Walking steps of two cattle in each plot (no./plot)
LC_cover： Plant cover of L. chinensis grass (%)
grass_cover： Plant cover of other grasses (%)
forb_cover： Plant cover of forbs (%)
n/a: No data available
Tab: behavior_experiment
Column Explanation
Year： Year of data collection in 2022
treatment： Three treatments in the grasshopper behavior manipulation experiment
Ungrazed: grasshoppers that were able to jumped in ungrazed plot
Grazed-Jumping: grasshoppers that were able to jump in grazed plots
Grazed-No Jumping: grasshoppers that were unable to jump in grazed plots
sample_time： Manipulation experiment was repeated three times
1= first time
2=second time
3=third time
sex: Gender of grasshoppers: male or female
Total_No： 50 male and 50 female grasshoppers were tethered by monofilament line of different length
No_killed_swallow： Number of grasshoppers killed by swallow
No_killed_cattle： Number of grasshoppers killed by cattle
Tre_oneway： Combined treatment and grasshoppers sex into one column:6 treatments in total.
Ungrazed_male
Grazed-Jumping_male
Grazed-No Jumping_male
Ungrazed_female
Grazed-Jumping_female
Grazed-No Jumping_female
Code/Software
All data were analyzed using the open-source software R version 4.3.0.
- Zhu, Yu et al. (2024), Behavioral responses to mammalian grazing expose insect herbivores to elevated risk of avian predation, , Article, https://doi.org/10.5281/zenodo.13160878
- Zhu, Yu et al. (2024), Behavioral responses to mammalian grazing expose insect herbivores to elevated risk of avian predation, , Article, https://doi.org/10.5281/zenodo.13160879