# Does size dimorphism reduce competition between sexes? The diet of male and female pine martens at local and wider geographical scales

> Male pine martens are about 40% heavier than females, but do they eat bigger prey? Using scats and snow-tracking in Poland’s Białowieża Forest, and diet studies from Russia, this study found that the sexes ate prey of similar size. Females climbed trees more and ate more squirrels and birds, while males ate more carcasses, so behaviour, not size, explained most of the difference.

Summary by Kersey Lawrence, Original Wisdom. Updated 9 November 2026. Page: https://www.originalwisdom.com/tracking-literature/2007-zalewski-does-size-dimorphism-reduce/

## Citation and access

- **Authors:** Andrzej Zalewski
- **Year published:** 2007
- **Journal or source:** Acta Theriologica
- **Full citation:** Zalewski, A. 2007. Does size dimorphism reduce competition between sexes? The diet of male and female pine martens at local and wider geographical scales. Acta Theriologica 52(3): 237–250.
- **DOI:** 10.1007/BF03194220
- **Access status:** Hosted (freely available elsewhere)
- **PDF:** https://www.originalwisdom.com/wp-content/uploads/2026/11/2007_Zalewski_does-size-dimorphism-reduce-competition-between-sexes.pdf

## Tags

- **Species:** Mammals > Pine marten
- **Region:** Europe > Poland
- **Tracking:** Scat; Snow tracks; Tracking; Tracks and signs identification; Trailing
- **Behaviour and ecology:** Behaviour; Competition; Feeding; Hunting; Scavenging
- **Methods and technology:** Literature review; Radio telemetry
- **Data type:** Existing data; New field data
- **Observer qualification:** Not reported
- **Discipline:** Behaviour and ecology; Wildlife tracking
- **Year published:** 2007

## Detailed keywords

- **Species:** Studied: European pine marten (Martes martes), males and females. Food remains found in scats: shrews; bank vole (Myodes glareolus, called Clethrionomys glareolus in Table 2); yellow-necked mouse and other Apodemus mice (Apodemus flavicollis, Apodemus spp.); voles (Microtus spp.); birch mouse (Sicista betulina) and harvest mouse (Micromys minutus); red squirrel (Sciurus vulgaris); hares (Lepus spp.); weasel (Mustela nivalis); mole (Talpa europaea); juvenile hedgehogs (Erinaceus concolor, Erinaceus sp.); ungulate carcasses (wild boar and deer named in the digestibility coefficients); small and large birds; amphibians, reptiles and fish; carabid beetles; wasps and wild bees; fruits, nuts, seeds, grass and fungi. Comparison species discussed: American marten (Martes americana), fisher (Martes pennanti), sable (Martes zibellina), polecat (Mustela putorius), stoat (Mustela erminea), mink (Mustela vison). Red fox scats are mentioned as a possible source of misidentified scats.
- **Location and habitat:** Białowieża National Park strict reserve (47.5 km²) and surrounding forest, Białowieża Primeval Forest, north-eastern Poland (52°43’N, 23°54’E), on the Polish-Belarusian border. Old-growth lowland deciduous and mixed forest: oak-lime-hornbeam (44.4% of the area), mixed coniferous (spruce and pine) and ash-alder forest, mean stand age 130 years, with many snags and large fallen logs. No trapping or hunting of predators; little human disturbance. Literature comparison: six winter diet samples from Poland (Białowieża) and Russia (Bashkirskii Reserve, Vologda region, north-eastern European Russia, and two from the Pechora river).
- **Topics:** sexual size dimorphism; niche variation hypothesis versus sexual selection hypothesis; food-niche partitioning between the sexes; intraspecific competition; diet composition by season (spring, summer, autumn-winter); rodent abundance cycles (high-moderate versus low years); prey size; food niche breadth and overlap; microhabitat use while foraging in winter; arboreal behaviour of females; geographical variation in diet; arboreal latrines at resting sites; prey identification from guard hairs (cuticle scales and medulla patterns).
- **Statistics or models:** t-tests (body size; snow-tracking foraging modes); log-linear analysis of prey frequency of occurrence (Białowieża data and the geographical comparison); Levins index of standardised food niche breadth; Pianka index of niche overlap; general linear models (GLM) for niche breadth, niche overlap and prey size; Erlinge’s (1987) prey size index. No Bonferroni correction was applied (the author explains why). Inconsistencies: the text says 506 scats from females, but the female sample sizes in Table 2 add up to 514 (the male sizes add up to the stated 697); the seasonal effect on prey size is given as F1 although three seasons were compared; the bank vole is called Myodes glareolus in the text and Clethrionomys glareolus in Table 2; Figure 2 shows four seasons (spring, summer, autumn, winter) while the analysis uses three.
- **Data type:** New field data: scats (697 from 8 males and 506 from 8 females, by the text) from resting sites of radio-tracked martens and from snow-tracking; snow-tracking of radio-marked martens (17 male and 11 female 250 m trail sections); body measurements from live-trapped animals and museum specimens collected 1961 to 2005. The years of scat collection and snow-tracking are not given; only one high rodent year was observed. Existing data: published winter diet studies of male and female pine martens from Russia (stomachs and/or scats).

## Synopsis

### 1. What they did

Male pine martens are much bigger than females. One idea is that this size difference lets the sexes eat different food, so they compete less. Another is that the size difference comes from males competing for mates, and any diet differences come from the sexes behaving differently. The author tested these ideas in Białowieża Primeval Forest, eastern Poland, where rodent numbers rise and fall from year to year with tree seed crops.

- Body size. Males and females were measured from live-trapped martens and museum specimens.

- Diet. Scats from radio-tracked martens of known sex were collected from latrines near their tree resting sites (mostly 10 to 25 m up in the trees) and during snow-tracking. Prey were identified from bone fragments, guard hairs and seeds, and diet was compared between the sexes across three seasons and in years of high-moderate and low rodent abundance.

- Foraging in winter. Radio-marked martens were snow-tracked, and everything they did along their trails was recorded, such as walking on or under fallen logs, climbing trees, entering cavities and attacking prey.

- A wider comparison. The author gathered all published winter diet studies that reported males and females separately, and compared six samples from Poland and Russia.

### 2. What they found

Size

- Males were 41% heavier and 11% longer than females (average 1.36 kg versus 0.96 kg).

Diet in Białowieża

- Small mammals, especially bank voles and yellow-necked mice, were the main food in both good and poor rodent years (in over 49% of scats).

- Birds, invertebrates and plant material were common in summer; ungulate carcasses were eaten mainly in autumn-winter.

- Overall, males ate more amphibians and reptiles, ungulate carcasses and plant material; females ate more squirrels and, in most seasons, more birds.

- When rodents were scarce, both sexes ate larger prey and a wider range of foods.

- Males and females did not differ in average prey size or in how broad their diets were.

- Diet overlap between the sexes was lowest in spring and in years when rodents were scarce.

Foraging in the snow

- Both sexes used fallen logs and root plates of fallen trees much more than standing trees, and in the same way.

- Females climbed standing trees more often than males. They also tended to enter cavities more often and travelled further in the tree canopy, but these differences were not statistically significant.

- Males attacked prey more often (1.00 versus 0.09 attacks per 250 m of trail).

Across Europe

- Diets differed greatly between the six populations.

- In every population, females ate more red squirrels and birds, and males ate more ungulate carcasses.

- Prey size varied between places but not between the sexes.

### 3. What they concluded

- Contrary to the niche variation idea, the larger males did not consistently eat bigger prey. Diet differences between the sexes are not the main cause of the size difference.

- Diet differences between the sexes change with food supply and place, and come mainly from behaviour: when and where each sex is active, which microhabitats they use, and how far they range.

- Smaller, lighter females may be able to follow squirrels across thin branches and gaps in the canopy, which may explain why they ate more squirrels and birds. Males, with larger home ranges, may be more likely to find patchy food such as carcasses and fruit.

- Overall, the size difference makes only a small contribution to diet separation, mainly by giving females easier access to prey in the trees.

### 4. How tracking was or was not used

Snow-tracking of radio-marked martens was used in two ways. First, the trails provided scats of known sex. Second, 250 m sections of trail were read to record how each marten foraged: walking along, on or under fallen logs and root plates, climbing standing trees, entering cavities, distance travelled in the tree canopy, and attacks on prey. Scats were also collected at arboreal latrines near resting sites found by radio-tracking. Fallen scats were collected only when fresh, to avoid mistaking fox scats for marten scats.

### 5. Tracker or observer certification

Not reported. Who did the snow-tracking and how the trail records were read is not described. The acknowledgements thank E. Bujko, A. Szymura and students from Farnborough College of Technology (England), Warsaw University and Jagiellonian University in Kraków (Poland) for help with field work.

### 6. Other technologies, skills or innovations

- Radio-tracking to find resting sites and to locate martens for snow-tracking.

- Prey identification from guard hairs (cuticle scales and medulla patterns), bone keys and a reference collection.

- Rodent abundance measured by removal trapping three times a year.

### 8. Implications for tracking (Original Wisdom's observations)

_These are Original Wisdom's observations, not the authors'._

- Snow-tracking let the author see how each sex actually foraged, such as how often females climbed trees and how often males attacked prey, behaviour that scats and radio locations alone could not show.

- Knowing which sex left a trail made it possible to link diet from scats to individual behaviour, a useful pairing of tracks and signs with laboratory work.

## Cite this summary

Lawrence, K. 2026. Summary of: Does size dimorphism reduce competition between sexes? The diet of male and female pine martens at local and wider geographical scales (Zalewski, 2007). Original Wisdom, Tracking Literature. https://www.originalwisdom.com/tracking-literature/2007-zalewski-does-size-dimorphism-reduce/