Analysis of predator's diet
The diet of predators as a tool for the study of small mammals
Nocturnal birds of prey and mesocarnivores are predators with a generalist diet and consume small mammals very frequently. Nocturnal birds of prey (owls, tawny owls, etc.), after swallowing their prey without crushing it, regurgitate the indigestible parts (hair and whole bones) in the form of compact balls, which are called pellets. In the case of mesocarnivores (genets, foxes, etc.), the remains of small mammals must be found in the feces and this makes diet analysis more complicated, since they are highly fragmented. Analyzing the feeding remains of predators provides information on species that are not very abundant, which would be difficult to obtain using other study techniques. For example, in the diet of the barn owl and the genet there are three times as many species (17-18 taxa) than in the live capture system carried out in the context of SEMICE monitoring (6 species).
In addition, diet analysis not only makes possible to obtain small mammals records, but also offers the possibility of estimating their abundance, since generalist predators change their diet based on the preys that are most available in the locality where they hunt. Thus, a certain species of small mammal will appear in a greater proportion in the diet as it is more abundant in the environment. This "indirect" study technique is quite exhaustive and offers many advantages over the "direct" technique, in which data on the species of small mammals are obtained from the observation of individuals, as would be the case of capture in traps. One of the great virtues of analyzing the diet is that the sample obtained is relatively heterogeneous, since it comes from droppings/pellets collected over fairly wide periods of time and space. Predators have large territories and hunt constantly, and the accumulation of their droppings in latrines and roosts facilitates the collection of representative samples and subsequent analysis.
A new web module for diet data entry
It aims to obtain data on the presence and abundance of small mammals in a non-invasive way, in order to complement the results obtained by means of the live trapping protocol. This new module, which is addressed to any volunteer or entity, makes it possible to collect and incorporate the small mammals and other species that are detected during the analysis of the content of pellets and droppings from their predators. If you want to upload your results, it is important that you register on the website and read the module's operating protocol.
Extra resources
Below we attach a series of extra resources that will help you to make a correct identification of the main species, including a training video recorded for the volunteers of the Atles de Mamífers de Catalunya.
- Clau de EgaEduca
- Clau de Gosàlbez i Arrizabalaga
- Manual per a la identificació de cranis de rosegadors (Jacinto Román)
Results
The map shows the distribution of the sampled localities grouped in the UTM grid of 10 Km on a side. By clicking the squares you get a summary with the number of localities, samples and detected species.
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Predators
The graph shows the percentage of samples analyzed based on the predator species.
Prey
The graph shows the percentage of individuals of each prey species that have been recorded.
Predator-prey relationship
The figures show the predator-prey relationship based on data recorded on the web. The thickness of the arrows is proportional to the number of interactions.
Visualization made by Esther Amores with drawings by Toni Llobet and Alfons Raspall
Long-eared Owl (Asio otus)
The short-eared owl (Asio otus) is a nocturnal bird of prey present in Europe, Asia and North Africa. It is a medium-sized bird, with a length of 34 to 39 cm and a wingspan of 86 to 98 cm. Short-eared owls have dark brown fur with white spots and a round face with two tufts of feathers that resemble ears. It is a solitary and territorial bird, preferring open forests, fields and grasslands. It feeds mainly on small mammals, such as mice, voles and shrews, but can also eat birds, insects and amphibians. The breeding season begins in March or April, depending on geographic location. The female lays 3 to 7 eggs in a nest built in a tree or in a natural cavity. The eggs hatch after about a month and the chicks remain in the nest for another 4-5 weeks before flying for the first time.
Tawny Owl (Strix aluco)
The Tawny Owl (Strix aluco) is a medium-sized owl species that is widespread across Europe, Asia, and North Africa. Tawny Owls have a plump body with a rounded head and large, dark eyes. They have reddish-brown or tawny plumage, which provides excellent camouflage in their woodland habitat. Their feathers are soft and allow for silent flight, enabling them to hunt stealthily.Tawny Owls are primarily woodland birds and are well-adapted to live in various types of forests, including deciduous, coniferous, and mixed woodlands. They can also be found in parks, gardens, and urban areas that have suitable trees for nesting and roosting. Tawny Owls are nocturnal hunters that mainly feed on small mammals, such as voles, mice, shrews, and rats. They are opportunistic predators and also consume birds, insects, amphibians, and occasionally fish. Tawny Owls are monogamous and form long-term pair bonds. They breed once a year, typically in late winter to early spring. The female lays 2-5 eggs in a nest made by modifying a tree hollow, often an abandoned nest of another bird. The incubation period lasts around 30 days, and both parents share the duty of incubating the eggs and raising the young.
Western Barn Owl (Tyto alba)
The barn owl (Tyto alba) is a nocturnal bird of prey found almost everywhere in the world, except in very cold regions and deserts. It is a medium-sized bird, with a length of 33 to 39 cm and a wingspan of 80 to 95 cm. Owls have light brown plumage with white spots and a heart-shaped face without ear-shaped feathers. They are solitary and territorial birds, which prefer open or semi-wooded landscapes, such as savannahs, grasslands, wetlands, peri-urban areas and rural forested areas. It feeds mainly on small mammals, such as mice, voles, shrews and rabbits, but can also eat birds, reptiles and insects. Owls are sedentary birds that breed in Europe, Asia and Africa. The breeding season begins in February or March depending on geographic location. The female lays 2 to 7 eggs in a nest built in a natural burrow or abandoned building. The eggs hatch in about a month and the chicks remain in the nest for another 6 to 7 weeks before flying for the first time.
Little Owl (Athene noctua)
The Little owl (Athene noctua) is a nocturnal bird of prey found in most of the warmer temperate regions of Europe, Asia, Korea and North Africa. It is a small bird, measuring 22 to 27 cm long and with a wingspan of 56 to 64 cm. Owls have light brown feathers with white spots and round faces without ear-like tufts. Solitary and territorial bird, which prefers open forests, fields, meadows, suburban areas and olive groves. They feed mainly on insects, worms, other invertebrates and small vertebrates, such as mice and lizards. The breeding season begins in March or April, depending on geographic location. The female lays 3 to 6 eggs in a nest built in a natural burrow or abandoned building. The eggs hatch after about a month and the chicks remain in the nest for another 4-5 weeks before flying for the first time.
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