The long-eared owls derives almost of its food energy from rodents.
Among this order, they are usually associated with a single group, the voles.
The life history of the long-eared owl is inexorably linked to voles.
Voles, members of the family Cricetidae and subfamily Arvicolinae, are often numerous, small-to-medium-sized rodents with relatively short tails.
In Europe, especially, the long-eared owl can be considered a specialized vole hunter.
Out of 86 prey studies in the continent, in about 69% voles made up more than half of the prey.
In particular, in the region of central Europe, a little over 82% of 57,500 prey items was made up of voles.
Where a variety of voles are available in Europe, long-eared owls show a preference for the most gregariously inclined common vole (Microtus arvalis) over the less sociable field vole (Microtus agrestis).
In central Europe, 76% of the diet was compromised by the common vole species alone.
More specifically, in the largest known study from Germany, of 45,439 prey items in the regions of Berlin and Nordharz, common vole accounted for 72%, with the field vole and tundra vole (Microtus oeconomus) collectively another 5.5%.
Another large representation of the common vole was in Slovakia, where they made up 84.1% of the diet (27,720 out of 32,192 total prey items).
In different years in Slovakia, common voles may range from as much as 92.4% to as little as 57.2% depending on vole numbers.
Locally, such as in former Czechoslovakia and in western Ukraine, about 94-95% of the diet may be common voles alone (of 4153 and 5896 prey items, respectively).
The dietary association with the common vole generally continues to most areas of European Russia, such as Moscow.
At times, such as indicated in Moldova, long-eared owls are capable of culling as much as 50% of the common vole population and it was opined that the voles would easily become pestilent to humans if not naturally controlled.
Like many voles, common voles are subject to population cycles.
In accordance with the cyclic nature of vole populations, the local numbers of long-eared owls can rise and fall sharply.
In low vole years, they tend to lay fewer eggs and feed fewer young, and may not attempt to breed at all.
In high vole years, they generally lay and hatch more eggs and rear more young.
While incubation starts with first egg, only the oldest siblings may be feed in low food years.
Generally various species of mice are eaten in poor years for common voles but appear to be an inefficient substitute (at least in more northerly climes) based on the owls’ lower breeding rates.
Apparently, common voles at times may collectively shift in temporal activity into more diurnal activity in what may be an attempt to mitigate heavy owl predation (especially as basically all European owls tend to hunt them), although several diurnal predators are nearly as specialized predators of them as well.
Evidence has indicated that common voles are altering their life cycles with unknown long-term results due likely to global warming.
It is likely that the long-eared owls of the region are to be effected by this but it is uncertain exactly what the resulting effect will be.

In some parts of Europe, common voles are at times not found or are locally infrequent or rare, especially on large islands, Scandinavia and some parts of the southern reaches, such as the Iberian Peninsula, Italy and Greece.
Therefore, long-eared owls live mostly on different prey species.
Supplemental or, occasionally, primary prey when voles are less common are murid rodents, especially the commoner genera such as Apodemus or field mice, Mus or house mice and, occasionally, Rattus or typical rats.
In Scandinavian studies, common voles were still the main prey in Finland where distributed (and outnumbered field voles in the owl's diet four-to-one) and partially in Denmark (where foods were split between the two commoner vole species and field mice) but are not in Sweden and Norway.
In Sweden, where common voles are not found, field voles were the main food, making up 65.2% of 13
The long-eared owls derives almost of its food energy from rodents. Among this order, they are usually associated with a single group, the voles. The life history of the long-eared owl is inexorably linked to voles. Voles, members of the family Cricetidae and subfamily Arvicolinae, are often numerous, small-to-medium-sized rodents with relatively short tails. In Europe, especially, the long-eared owl can be considered a specialized vole hunter. Out of 86 prey studies in the continent, in about 69% voles made up more than half of the prey. In particular, in the region of central Europe, a little over 82% of 57,500 prey items was made up of voles. Where a variety of voles are available in Europe, long-eared owls show a preference for the most gregariously inclined common vole (Microtus arvalis) over the less sociable field vole (Microtus agrestis). In central Europe, 76% of the diet was compromised by the common vole species alone. More specifically, in the largest known study from Germany, of 45,439 prey items in the regions of Berlin and Nordharz, common vole accounted for 72%, with the field vole and tundra vole (Microtus oeconomus) collectively another 5.5%. Another large representation of the common vole was in Slovakia, where they made up 84.1% of the diet (27,720 out of 32,192 total prey items). In different years in Slovakia, common voles may range from as much as 92.4% to as little as 57.2% depending on vole numbers. Locally, such as in former Czechoslovakia and in western Ukraine, about 94-95% of the diet may be common voles alone (of 4153 and 5896 prey items, respectively). The dietary association with the common vole generally continues to most areas of European Russia, such as Moscow. At times, such as indicated in Moldova, long-eared owls are capable of culling as much as 50% of the common vole population and it was opined that the voles would easily become pestilent to humans if not naturally controlled. Like many voles, common voles are subject to population cycles. In accordance with the cyclic nature of vole populations, the local numbers of long-eared owls can rise and fall sharply. In low vole years, they tend to lay fewer eggs and feed fewer young, and may not attempt to breed at all. In high vole years, they generally lay and hatch more eggs and rear more young. While incubation starts with first egg, only the oldest siblings may be feed in low food years. Generally various species of mice are eaten in poor years for common voles but appear to be an inefficient substitute (at least in more northerly climes) based on the owls’ lower breeding rates. Apparently, common voles at times may collectively shift in temporal activity into more diurnal activity in what may be an attempt to mitigate heavy owl predation (especially as basically all European owls tend to hunt them), although several diurnal predators are nearly as specialized predators of them as well. Evidence has indicated that common voles are altering their life cycles with unknown long-term results due likely to global warming. It is likely that the long-eared owls of the region are to be effected by this but it is uncertain exactly what the resulting effect will be.
In some parts of Europe, common voles are at times not found or are locally infrequent or rare, especially on large islands, Scandinavia and some parts of the southern reaches, such as the Iberian Peninsula, Italy and Greece. Therefore, long-eared owls live mostly on different prey species. Supplemental or, occasionally, primary prey when voles are less common are murid rodents, especially the commoner genera such as Apodemus or field mice, Mus or house mice and, occasionally, Rattus or typical rats. In Scandinavian studies, common voles were still the main prey in Finland where distributed (and outnumbered field voles in the owl's diet four-to-one) and partially in Denmark (where foods were split between the two commoner vole species and field mice) but are not in Sweden and Norway. In Sweden, where common voles are not found, field voles were the main food, making up 65.2% of 13
Long-eared owl