Individual diet specificity under abnormal prey supply (Naliboki Forest)

Before 2013, roe deer reached high population densities in the Naliboki Forest (on average 398 roe deer/100km²). Under these conditions lynxes were almost entirely specialized in feeding on roe deer.

To study the individual diet of lynx, we analysed 127 scats in total in the area, where 5-8 lynxes lived: 53 from the cold season (CS) and 74 from the warm season (WS). In the warm season the frequency of occurrence (%FO) of roe deer amongst prey was 96.3%, and in the diet in terms of biomass consumed (%BC) the portion of roe deer was 81.2%. In the cold season the frequency of occurrence of roe deer amongst the prey taken  was 89.0% and in the diet in term of biomass consumed the portion of roe deer was 83.5%.

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In those years in Naliboki Forest, while snowtracking lynxes, we found that in winter, an adult male lynx killed about one roe deer per about 6 days on average, an adult female with two kittens killed one roe deer per 4-5 days.

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An extended period with deep snow in late winter and early spring 2013 caused a crash of the roe deer population in Naliboki Forest. Since then we noticed differences in individual feeding patterns of lynxes. From November 2013 until mid-December 2017 (in conditions of low roe deer density) we learnt the following examples from individual lynx diet analysis in the conditions, when roe deer density was low:

adult male (Kazimir) (196 scats; 144 in CS and 52 in WS ): beaver (29%BC), hare (14%BC), wild boar (12%BC), raccoon dog (12%BC), red deer (11% BC), roe deer (10%BC), squirrel (5% BC), rodents (3% BC), red fox (1% BC), pine marten (<1% BC), hedgehog (<1%BC), hazel grouse, mallard and small birds (2% BC);

adult female (Marysja) with one kitten (69 scats in CS): still specialized in feeding on roe deer (71%BC), other food items were hazel grouse and other small birds (11%BC), red squirrel (6%), small rodents (5%BC), mountain hare (4%BC), raccoon dog (2%BC) and red fox (1%BC); this family lived in the core area of Kazimir, and, so, faced with the same prey abundance and availability, but had a distinctive diet;

adult female without litter or with 2 kittens (Hanna) (94 scats; 34 in CS, 60 in WS): red deer and roe deer (19%BC), small rodents (8%BC), red squirrel (4%BC), beaver (13%BC), raccoon dog (5%BC), red fox (1%BC), muskrat (1%BC),  hare (24%BC), hedgehog (4%BC), pine marten (<1%BC), American mink (<1%BC), owls (<1%BC), hazel grouse (3%BC), capercaylie (6%BC), mallard (4%BC), small birds (7%BC); this family lived in the core area of Kazimir, and, so, faced with the same prey abundance and availability, but had a distinctive diet;

adult female (Jadz’viha)  with 2-3 kittens during three consecutive years (177 scats; 154 in CS, 23 in WS ): roe deer (65%BC), hare (10%BC), small rodents (7%BC), grouses and other birds (6%BC), wild boar (4%BC), small rodents (7%BC), red squirrel (<1%BC) and hedgehog (<1%BC).

adult male (Stiapan) (122 scats; 71 in CS, 51 in WS): mainly red deer, but also roe deer (59%BC), grouses, ducks and small birds (29%BC),  hare (5%BC), beaver (3%BC), red fox (2%BC), raccoon dog (<1%BC), small rodents (1%BC), hedgehog (<1%BC), red squirrel (<1%BC);

adult male (Bazyl’) (57 scats; 21 in CS, 36 in WS): red deer and roe deer mostly (59%BC), beaver (4%BC), grouses and mallards (17%BC), hares (10%BC), red squirrel (2%BC), hedgehog (1%BC), badger (1%BC), small rodents (3%BC), red fox (2BC%), raccoon dog (1%BC), small birds (<1%BC).

Thus, we may characterize feeding of the model lynxes by the following way.  Kazimir was a generalist predator on mammals, mainly on medium-sized mammals as beaver, wild boar, red deer, roe deer and raccoon dogs.  Marysja was still specialised in feeding on roe deer,  but she stayed in Kazimir’s core area, where he was generalist on mammals. Hanna was a generalist predator on a high diversity of mammals and birds, but she too stayed in Kazimir’s core area, where he was generalist on mammals. Hanna mainly lived, where Marysja stayed a year before and fed on roe deer mainly. The roe deer number did not  decrease, but Hanna relied on them markedly less and took a high diversity of prey species:mammals and birds of various sizes. Jadz’viha was a mammal eater, and nearly specialised in predating roe deer. Stiapan demonstrated a diversified predator diet consisting mainly of red deer and birds (mostly mallard and grouses).  The same may be said about Bazyl’.

Since the autumn of 2017 in Naliboki Forest the roe deer population has almost recovered after the crash during the early spring of 2013. Nevertheless, by studying their diets we see that lynxes still haven’t made the switch to being specialized roe deer predators. If we pool all scats from the different lynxes (59 scats were roughly analyzed) we see that nearly half of all scats (actually 28) contained roe deer and red deer remains only. We think, it will take a few years before lynxes return to their specialized feeding after the roe deer (as a preferenced prey) population recovered.

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