Warta Mouth National Park’ mammals record includes 39 species. Among them 6 belong to insectivores order (Insectivora), 2 species belong to the chiroptera (Chiroptera) order (this order requires further research in this area), 1 species from lagomorpha (Lagomorpha) order, 14 species of rodents (Rodentia), 11 species from the carnivore (Carnivora) order and 5 species from the artiodactyls (Artiodactyls) order.
Because of the Parks profile many of the mammals dwelling here are adapted to a ground and water lifestyle, like:
- the insectivore Water Shrew (Neomys fodiens) which saliva contains poison paralyzing its pray, water invertebrates, snails, amphibians, small fish. Very characteristic for water shrew are its hairy back limbs and tail, forming the so called keel, which facilitates swimming.
- Beaver (Castor fiber) is a herbivorous animal closely related to water, thus the Park’s rich hydrological net is extremely convenient for this species. It builds very numerous dams, in order to stop water outflow in some places, and beaver lodges where it lives. In spring these loges are used by graylag geese as platforms to build nests.
- herbivorous rodents like, Muskart (Ondarta zibethica) and European Water Vole (Arvicola terrestris), as opposed to Beaver, are decreasing in number over the last few years. It is probably related to the abundance of American Mink that hunts them. Muskart is an alien species, brought by human to Europe, whereas European Water Vole is a domestic species
- Otter (Lutra lutra) is a deftly swimming predator which takes advantage from the water environment where it finds food (fish, amphibians, invertebrates) as well as place for shelter and play, as even adult individuals like to play. It seems that the local otter population is slightly increasing.
The complex hydrological net of the Park is an ideal environment for water-depending animals. Watercouses as well as reservoirs are places where some dwelling here species feed, shelter and rest and these are:
- American Mink (Mustela vison) which basically eats fish hunted in the watercourses and stagnant reservoirs. Very crucial for mink’s diet are also birds and their eggs, amphibians and small mammals. Mink is a deft swimmer, tree climber and an very inteligent animal, thus as an alien species it constitutes a big danger for Polish fauna, especially for water birds. The nearby mink farms affect positively its population increase, as the escaping individuals supply the wild population.
- North American Racoon (Procyon lotor) is a clever alimentary opportunist. Its diet is mainly composed of small mammals, amphibians, water invertebrates i.e. fauna bound rather with water environment. North American Racoon eats also plants and sometimes even garbage produced by human. As an alien species, artificially introduced by human, it is a potential danger for the local fauna and flora and may cause disturbance of ecological balance.
- European Polecat (Mustela putorius) willingly chooses habitats with watercourses and reservoirs, as its crucial food component are amphibians. In the winter season this mammal frequently appears close to water as at the bottom of water reservoirs hibernate amphibians, which constitute up to 90% of European polecat’s food in this season.
Very characteristic of the Park are open spaces, composed mainly of agriculturally used grasslands and pastures (mowing, pasturing) and wastelands frequently overgrown by about 4 meters high reeds. This habitat is prefered by the local ungulate mammals like, Deer, Roe Deer and Wild Boar. The biggest among them, Deer (Cervus elaphus), despite the shortage of forests, which are their basic habitat, perfectly adapted to the local conditions. Deer in Warta Mouth National Park, after populating the small patches of the swampy forest (carr and alder swamp), as a result of lack of a proper habitat, started to spread to the nearby areas. These terrains are a mosaic of wet meadows, herbaceous communities and rushes (including reed beds that are very important for this species), however the two first habitats are a food base and the last one is a shelter place. At the brink of reed beds, in autumn begins a spectacular show, rut. At this time you may hear single adult Deers which compete with each other to attract females (doe) by giving characteristic noises. In late autumn you can observe herds of does, sometimes composed of many individuals with this year’s fawns. Deer’s population in the Park is estimated at 150 individuals, and increases a little, but permanently.
The smaller ungulate, Roe Deer (Capreolus capreolus), is here definitely more numerous than Deer. Roe Deer population stays relatively stable, however within the recent years some fluctuations have been observed. Presently, Roe Deer population is estimated at 450 individuals. Roe Deer, similar to Deer, uses habitats primordial for this species i.e. open terrains. In winter Roe Deers form herds of few dozens of individuals in order to survive the hard winter season when rather small Roe Deers have difficulties in moving in snow and finding food. That is why at this time they frequently fall prey to predators.
Wild Boar (Sus scrofa), the last from the here described ungulate mammals, is quite abundant in the Park, however its population decreased during last years (2008 – about 400 individuals, 2009 – about 300 individuals). Very characteristic of the local Wild Boars is that adult individuals are quite small, what is probably bound with poor quality of the available food. Like the above mentioned ungulate mammals, Wild Boar uses the available habitats i.e. a mosaic of wet meadows, rushes and forests. A very frequent and characteristic sign of Wild Boar presence are the places where these animals rooted up the earth while searching for food.
Wide meadows are favorable for a very diverse fauna of small mammals. Numerous populations of Common Shrew (Sorex araneus), Root Vole (Microtus oeconomus) and Striped Field Mouse (Apodemus agrarius) are recorded in the Park. These small mammals are a rich food base for animals appearing in the Park, birds (e.g. owls, day birds of pray and shrikes) as well as mammals. They are also an especially important diet component for canidae mammals, like Fox (Vulpes vulpes) and the alien Racoon Dog (Nyctereutes procyonoides) as well as weasels: Pine Marten (Martes martes), Beech Marten (Martes fina), Ermine (Mustela erminea) and Least Weasel (Mustela nivalis). The number of Fox and Raccon Dog is quite hight in the Park, because both species have an ability to adapt to different habitats. In this area, like in other parts of Poland, they most willingly choose more dry places with trees and bushes where the ground let them to dig a burrow. Wesels’ number in the Park is rather of medium value, but it tends to change.
In Warta Mouth National Park appear three alien species: American Mink, North American Racoon and Racoon Dog. First two ones have been brought here by human from North America and the last one comes from the Far East.
All the mentioned species are a potential or real danger for domestic fauna and flora. Currently Park’s employees conduct a research on the ecology and influence of these species on the local environment.