# Brown bears possess anal sacs and secretions may code for sex

> Do brown bears have scent glands under their tails? Anatomists had disagreed for decades. Researchers in Sweden checked 17 wild bears and found paired anal sacs in every one, holding a clay-like secretion of 90 compounds whose mix likely tells other bears whether a male or a female passed by.

Summary by Kersey Lawrence, Original Wisdom. Updated 9 November 2026. Page: https://www.originalwisdom.com/tracking-literature/2011-rosell-jojola-brown-bears-possess-anal/

## Citation and access

- **Authors:** Frank Rosell, S. M. Jojola, K. Ingdal, B. A. Lassen, J. E. Swenson, J. M. Arnemo and A. Zedrosser
- **Year published:** 2011
- **Journal or source:** Journal of Zoology
- **Full citation:** Rosell, F., Jojola, S. M., Ingdal, K., Lassen, B. A., Swenson, J. E., Arnemo, J. M. and Zedrosser, A. 2011. Brown bears possess anal sacs and secretions may code for sex. Journal of Zoology 283(2): 143–152.
- **DOI:** 10.1111/j.1469-7998.2010.00754.x
- **Access status:** Hosted (freely available elsewhere)
- **PDF:** https://www.originalwisdom.com/wp-content/uploads/2026/11/2011_Rosell_and_Jojola_etal_brown-bears-possess-anal-sacs-and-secretions-may-code-for-sex.pdf

## Tags

- **Species:** Mammals > Brown bear
- **Region:** Europe > Sweden
- **Behaviour and ecology:** Behaviour; Communication
- **Methods and technology:** Mann–Whitney U test
- **Data type:** New field data
- **Observer qualification:** Not needed
- **Discipline:** Behaviour and ecology
- **Year published:** 2011

## Detailed keywords

- **Species:** Studied: brown bear (Ursus arctos), 17 free-ranging, sexually mature bears (5 males and 12 females). Compared with other species from the literature: giant panda (Ailuropoda melanoleuca), American black bear (Ursus americanus), domestic dog (Canis familiaris), wolf (Canis lupus), spotted hyena (Crocuta crocuta), Eurasian beaver (Castor fiber), North American beaver, European badger (Meles meles), aardwolf, wolverine (Gulo gulo), steppe polecat (Mustela eversmanii), Siberian weasel (Mustela sibirica) and coyote (Canis latrans).
- **Location and habitat:** Dalarna and Gävleborg counties, south-central Sweden (61°N, 14°E), in the southern part of the Scandinavian brown bear population, at about 30 bears per 1000 km². Forest dominated by Scots pine (Pinus sylvestris), with Norway spruce (Picea abies), birches (Betula spp.), aspen (Populus tremula) and lodgepole pine (Pinus contorta). Intensive clearcut forestry, roads, bogs and lakes make a patchy landscape. Home ranges in the study area: male 1055 km², female 217 km².
- **Topics:** anal sacs and anal gland secretion (AGS); olfactory communication; scent marking; chemical coding of sex; digital coding (presence or absence of compounds) and analog coding (relative amounts); secretion colour; long-lasting scent marks and low-volatility (heavy) compounds; mating season; anatomy (anal sacs similar to the domestic dog’s); marking trees and rubbing behaviour; Scandinavian Brown Bear Research Project. Inconsistencies in the paper: (1) the methods give the 2008 sampling period as 6 to 30 April, but Table 1 dates one female’s sample (W0004) to 24 May 2008; (2) the abstract says male and female secretions differ in “possibly color”, while the discussion says the results supported a colour difference.
- **Statistics or models:** gas chromatography–mass spectrometry (GC–MS); partial least squares regression (PLSR, PLS1) with leverage correction, validated R² and root mean square error of prediction (RMSEP), in The Unscrambler 9.7; hierarchical cluster analysis with squared Euclidean distance; Mann–Whitney U test (SPSS 15.0); significance at P < 0.05, with 0.05 to 0.1 called marginally significant.
- **Data type:** New field data: secretion samples taken from bears captured by helicopter before the mating season, 18 April to 18 May 2007 and 6 to 30 April 2008, then analysed in the laboratory.

## Synopsis

### 1. What they did

Many carnivores leave scent marks with secretions from glands near the anus, and these secretions can carry information such as sex, age and individual identity. For bears other than the giant panda, almost nothing was known, and earlier anatomists disagreed about whether brown bears even have anal sacs.

As part of a long-term project in south-central Sweden, the researchers darted free-ranging brown bears from a helicopter before the mating season in 2007 and 2008. While each bear was immobilized, they found the anal sacs by sight and by feeling for them, and squeezed out secretion from each sac, wearing latex gloves so their own scent did not contaminate the samples.

They then:

- Compared colour. They matched each secretion against a standard colour chart and also ranked it by eye from 1 (light) to 12 (very dark).

- Analysed the chemistry. They separated and tentatively identified the compounds in each sample with gas chromatography–mass spectrometry (GC–MS), a laboratory method that splits a mixture into its parts.

- Tested for sex differences. They asked whether males and females differed in the overall chemical profile, in the number of compounds, in which compounds were present, and in how much of each compound there was.

Samples came from 17 sexually mature bears (5 males and 12 females, aged 3 to 18 years). Some chemical data were lost, so the compound-by-compound comparisons used 4 males and 7 females.

### 2. What they found

Anatomy

- Every captured bear had a pair of anal sacs. Their layout is similar to the domestic dog’s, with a duct from each sac opening on either side of the anal canal.

- The secretion was clay-like with an unpleasant smell. The researchers could not smell any difference between males and females.

Colour

- Colour ranged from nearly black to light grey.

- Male secretion was on average darker than female secretion, but the two overlapped.

Chemistry

- They found 90 different compounds, mostly fatty acids, hydrocarbons and steroids. Cholesterol was by far the largest part, about 77% to 81% of the measured compounds on average.

- Of the compounds with a known molecular weight, 68% were heavy (above 300), the kind that evaporates slowly.

- Males had 74 different compounds in total and females 59, but the number per bear did not differ significantly between the sexes. They found no sex-specific compound (one present in every bear of one sex).

- Overall chemical profiles tended to separate males from females.

- The amounts of five shared compounds, all steroids, differed: females had more of four of them, and males had somewhat more of one (a marginal result).

- Grouping bears by which compounds they had did not separate males from females.

Timing

- The amount of secretion that could be squeezed out seemed to decrease as the mating season went on (a personal communication from a project member, not measured in the study).

### 3. What they concluded

- This is the first study to confirm conclusively that brown bears have anal sacs, and the first to analyse their secretion chemically.

- The secretion likely carries information about sex, through the mix and relative amounts of several compounds rather than any single male or female compound. It probably carries other information that matters to the bears’ social life too.

- Colour overlaps between the sexes, so colour alone should not be used to tell a bear’s sex.

- The many heavy, slow-evaporating compounds suit long-lasting scent marks, useful for a solitary animal with a very large home range.

- Bears may use the secretion more to advertise their presence in the mating season, when they are more likely to meet, though lower production after the mating season is also possible.

- The authors think it likely, but unknown, that brown bears can release the secretion separately from their droppings, as wolves can.

- They mention that bears have been seen to sit down in front of trees after rubbing them, and often sniff the ground before rubbing (a personal communication), which suggests the secretion may be used in marking.

- Future studies should look at differences between age groups.

### 6. Other technologies, skills or innovations

- Helicopter darting and immobilization of free-ranging bears; age from tooth cementum layers.

- Gas chromatography–mass spectrometry with a library of about 70,000 known compounds; unidentified compounds were added to a new library so they could be recognized across samples.

- Partial least squares regression, a statistical method suited to many closely related measurements from few animals.

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

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

- Trackers reading bear rub trees and marking sites may find this useful background: the study shows that brown bears carry a scent source near the anus that likely signals sex, and the authors link it to bears sitting down in front of trees after rubbing. The study did not examine marks in the field.

## Cite this summary

Lawrence, K. 2026. Summary of: Brown bears possess anal sacs and secretions may code for sex (Rosell and Jojola et al., 2011). Original Wisdom, Tracking Literature. https://www.originalwisdom.com/tracking-literature/2011-rosell-jojola-brown-bears-possess-anal/