The study, published in the journal Metabarcoding and Metagenomics, analysed the diet of sixteen maternity colonies spread across the northern Iberian Peninsula and southern France, the heart of the species’ western European range. Using DNA metabarcoding on 318 faecal samples collected in May and July of 2020, the researchers identified 241 prey species belonging to 97 families and 16 orders. The results confirm what smaller studies had hinted at: orb-web building spiders are the notch-eared bat’s most important prey, followed by diurnal pest flies associated with livestock farming.

Spiders dominated the diet with a weighted percentage of occurrence of 52 percent and appeared in 83 percent of samples. Among them, the European garden spider (Araneus diadematus) was the single most consumed species, particularly in July. House flies (Musca domestica) ranked second overall, followed by stable flies (Stomoxys calcitrans), both notorious livestock pests. Together, spiders and flies accounted for 68 percent of the total dietary composition, reinforcing the bat’s reliance on gleaning — a slow, manoeuvrable hunting style that allows it to snatch prey resting on substrates rather than chasing flying insects.

The research team, led by N. Vallejo and colleagues, collected samples from colonies ranging from 30 to 800 individuals, all roosting in buildings across climatic profiles stretching from temperate oceanic to Mediterranean. They characterized the landscape within a 10-kilometre radius of each colony using Sentinel-1 and Sentinel-2 satellite data, reclassifying land uses into forests, non-forested natural areas, pastures, croplands, urban areas and water bodies. Official cattle census data from Spain and France allowed them to estimate both the total number of cows and the mean number per farm around each roost.

Seasonal patterns emerged clearly. Dietary diversity was significantly higher in May at all taxonomic levels, while the proportion of spiders in the diet increased significantly from May to July. The researchers attribute this decline in diversity to higher prey availability in late summer, allowing bats to become more selective and specialize in the most profitable items. Spider species richness was also higher in May, and Mediterranean colonies showed greater spider richness in their diet, likely reflecting richer arthropod communities and a broader range of foraging habitats including scrublands and semi-open natural areas.

The most striking finding concerns the relationship between pest fly consumption and livestock. Using a hurdle model designed for zero-inflated data, the researchers found that the probability of consuming diurnal flies increased significantly with the number of cattle near the colony, with consumption becoming likely once cattle numbers exceeded roughly 2,000 heads within the 10-kilometre radius. In areas where cattle farming was negligible, fly consumption was none or minimal — contradicting the assumed dependence of northern notch-eared bat populations on livestock farming.

Yet once fly consumption occurred, its relative importance in the diet was not related to cattle numbers. Instead, forest cover and urban areas shaped the weighted percentage of occurrence of pest flies. Higher forested area reduced the importance of flies in the diet, likely because forests provide alternative prey such as spiders, moths and beetles that increase dietary diversity. Urban areas had the opposite effect: as natural prey declines with urbanization, bats appear forced to forage more intensively on cattle sheds, exploiting their original gleaning behaviour in a new context.

This behavioural plasticity is remarkable for a species with a relatively narrow trophic niche compared to other European bats. Previous studies in the Basque Country found that five nursing colonies focused on no more than a dozen prey species throughout their active season, with spiders and flies accounting for around 80 percent of total prey volume. The new research confirms this consistency across a much larger geographical and climatic range, from oceanic northern Spain to the Mediterranean south.

The predator-prey interaction between the notch-eared bat and livestock pest flies carries practical implications. Both stable flies and house flies are epiparasitic, harming cattle, transmitting viral and bacterial diseases and reducing milk production. The researchers suggest the notch-eared bat presents an interesting opportunity for integrated pest management strategies in Europe, though quantifying the predation pressure a single colony can exert remains challenging given the complex interplay between fly consumption, geography, climate and landscape characteristics.

The authors conclude that conservation efforts for the notch-eared bat should go beyond protecting forests alone. Because spiders common in semi-open Mediterranean habitats — such as Argiope bruennichi and Cyclosa algerica — are important prey, management should focus on broad-scale preservation of a variety of native habitat types and their associated arthropod communities. Meanwhile, restricting bats’ access to cowsheds would negatively impact pest fly profitability, and colonies would be most vulnerable if suitable sources of pest flies disappear while surrounding natural habitats are also degraded.

Subject of Research: DNA metabarcoding of notch-eared bat faeces across 16 Iberian and French colonies reveals orb-web spiders as the dominant prey and links livestock pest fly consumption to cattle density, forest cover and urbanization.

Article Title: DNA metabarcoding reveals the influence of land cover and farming on the dietary composition of a spider-specialist bat

Article References: Vallejo, N., Aldasoro, M., Olasagasti, L., Aihartza, J., & Garin, I. (2025). DNA metabarcoding reveals the influence of land cover and farming on the dietary composition of a spider-specialist bat. Metabarcoding and Metagenomics, 9, Article e144371. https://doi.org/10.3897/mbmg.9.144371

Image Credits: AI Generated

DOI: 10.3897/mbmg.9.144371

Keywords: bats, DNA metabarcoding, notch-eared bat, spiders, livestock pest flies, agriculture, land cover, gleaning, Iberian Peninsula, conservation, metabarcoding, reveals

The study’s central contribution is to quantify, at a scale rarely attempted, the relationship between seagrass-associated fishing and household poverty. Survey teams working across community networks in Southeast Asia, Melanesia and the western Indian Ocean gathered household-level data on income, food consumption, fishing effort and habitat use. By combining these social surveys with ecological assessments of seagrass extent and condition, the researchers were able to estimate what share of household income and nutrition flows directly from seagrass fisheries, and how that share varies with household wealth. The answer, they report, is striking: in many communities, seagrass-adjacent fishing contributes a substantial portion of the protein consumed by the poorest quartile of households, far exceeding its contribution to wealthier families in the same villages.

This pattern reflects the particular ecological and economic character of seagrass systems. Unlike offshore fisheries that require boats, fuel and capital, seagrass meadows sit within walking distance of shore, accessible at low tide and by canoe, gleaning and hand-collection. Women, children and landless households — groups often excluded from formal fisheries statistics — harvest fish, octopus, clams, sea cucumbers and other invertebrates from these shallow grounds. Because seagrass fishing requires little investment, it functions as what economists would call a poverty buffer: a low-barrier resource that families fall back on when crops fail, fish prices collapse or formal employment disappears. The new analysis shows that this buffering role intensifies precisely when households are most vulnerable.

The technical core of the study lies in its integration of household survey data with habitat mapping across such a broad geographic range. Rather than studying a single village or country, the team assembled a comparative dataset spanning 156 communities, allowing them to distinguish local idiosyncrasies from regional patterns. They constructed indicators of household poverty that combine income measures with dietary diversity and asset ownership, and then modeled the association between dependence on seagrass-associated fishing and these poverty indicators. Statistical controls for community size, market access, reef and mangrove proximity, and fishing pressure helped isolate the specific contribution of seagrass habitats. The consistency of the signal across dozens of independent communities strengthens the case that the pattern is structural rather than incidental.

Why has this dependence remained so poorly documented? The researchers point to a combination of institutional blind spots. Official fisheries statistics in most countries are designed around landed catches brought to ports and markets, categories that capture trawl and purse-seine activity but miss gleaning and subsistence harvesting. Seagrass meadows, meanwhile, have historically received a fraction of the scientific and philanthropic attention devoted to coral reefs and mangroves, and they remain largely absent from marine protected area networks. Conservation planning in the region has often prioritized biodiversity targets and carbon storage goals without systematic assessment of who depends on which habitats for subsistence. The result is a policy landscape in which an ecosystem supporting millions of the world’s poorest coastal residents is managed, at best, incidentally.

The poverty dimensions of this oversight carry real consequences. When marine protected areas are established around seagrass beds without provision for continued access, or when seagrass meadows are degraded by coastal development, dredging, anchoring and land-based pollution, the resulting losses do not fall evenly across communities. Wealthier households can shift to other incomes, buy protein at markets or relocate fishing effort offshore. Poorer households, the study shows, have fewer alternatives and face immediate nutritional and financial harm. In effect, conservation interventions that appear ecologically neutral can function as regressive shocks, transferring costs from the global benefits of biodiversity protection onto the local poor. The authors frame this as a matter not only of food security but of distributional justice in environmental policy.

The findings also complicate a common conservation narrative in which protecting habitats automatically protects fisheries. Seagrass meadows do support juvenile fish, sequester carbon, stabilize sediments and improve water quality, and safeguarding them is essential to the long-term productivity of tropical coastal waters. But the study emphasizes that habitat protection and livelihood protection are not the same thing. A closed area may allow seagrass biomass to recover while simultaneously cutting off the poorest fishers from the resource, unless access rules, seasonal rotations or alternative livelihoods are built into the design. The researchers argue that conservation effectiveness and social outcomes must be evaluated together, and that the households most dependent on a habitat should be identified before management decisions are made, not after harm has occurred.

Methodologically, the study demonstrates the value of coupling fine-grained social measurement with ecological data across large spatial scales. Poverty is multidimensional, and its relationship to ecosystem use is context-dependent, shaped by tenure arrangements, gender norms, market access and seasonal dynamics. By aggregating standardized surveys across 156 sites, the team produced findings robust enough to inform regional policy while retaining the community-level resolution needed to target interventions. The approach offers a template for other ecosystems — mangroves, floodplains, dry forests — where reliance by poor households is suspected but poorly quantified. In each case, the same question applies: which households lose what when the habitat is degraded or closed, and can any compensatory mechanism realistically reach them?

The policy implications are concrete. The authors call for seagrass ecosystems to be explicitly incorporated into national fisheries assessments, poverty reduction strategies and marine spatial planning. They urge that gleaning and shallow-water harvesting — activities dominated by women and marginalized groups — be recognized in fisheries governance rather than treated as informal residue. And they recommend that marine protected area design in seagrass regions adopt social safeguards comparable to those used in terrestrial conservation, including participatory zoning, temporary rather than permanent closures, and monitoring of household nutrition alongside ecological indicators. Without such measures, they warn, marine conservation risks widening the very inequalities that undermine long-term stewardship, as communities excluded from resources have little incentive to protect them.

For the millions of people living in poor coastal settlements across the Indo-Pacific, the study gives statistical weight to something they have long known: the green meadows beneath the shallows are not scenery but supper, savings and insurance. As nations negotiate global biodiversity targets and blue economy investments, the research serves as a reminder that the ocean’s contributions to people are distributed unevenly, and that counting them accurately is a prerequisite for conserving them fairly. What happens to seagrass, the study concludes, is inseparable from what happens to the world’s coastal poor — and marine conservation will only succeed as a global enterprise when it learns to see, and protect, both at once.

Subject of Research: The relationship between seagrass-associated fishing and household poverty across Indo-Pacific coastal communities

Article Title: Seagrass fisheries expose the poverty dimensions of marine conservation

Article References: Jones, B. L. H., Unsworth, R. K. F., Ambo-Rappe, R., Carli, F., Coals, L., Digdo, A. A., Eklöf, J. S., Jiddawi, N. S., La Nafie, Y. A., Lopez, M. R., Nordlund, L. M., Septiani, C., Udagedara, S., & Cullen-Unsworth, L. C. (2026). Seagrass fisheries expose the poverty dimensions of marine conservation. Nature Sustainability. https://doi.org/10.1038/s41893-026-01932-6

Image Credits: AI Generated

DOI: 10.1038/s41893-026-01932-6

Keywords: seagrass, marine conservation, poverty, Indo-Pacific, fisheries, coastal livelihoods, food security, marine protected areas, gleaning, ecosystem dependence, blue economy, household surveys