Love in a time of social distancing

The berries have started to ripen and the days have begun to shorten. We are entering another phase in the year of the pine marten.

Kit independence

As the boisterous furry wombles (A.K.A. pine marten kits) begin to contemplate their gap years and heading out into the big wide world alone, mum finally gets to take a breather. I suspect she will be having a long foot soak, a G & T and watching two seasons of Poldark on Netflix. But this peace and tranquility will not last long, because its mating season!

Now, let us not forget lessons from previous blogs. Pine marten kits may not leave their mother for a whole year, so while she is being pestered by numerous males coming into her territory, she is also being pestered by her offspring. Nevertheless, summer is when females have their oestrus cycle, i.e. they come into season and are ready to mate1. Hopefully by this point she has regained some body condition after weaning the kits off her milk. However, at this time of year, females do tend to look a bit worn out and scraggly.

Same same but different

Pine martens display differences in size between males and females. This is what’s known as sexual dimorphism. In other species such as lions or deer this is much more pronounced with manes or antlers. But in martens the main difference is in length and weight, with the males coming out longer and heavier2.

Terry Whittaker

Mating

The females will be sexually receptive for a few days, on and off over the summer months and the characteristic scent marking of martens signals to males in the vicinity that mating season has begun. During this time of year, males will roam much further afield to find and mate with as many females as possible3. Both males and females are promiscuous and will mate with multiple individuals over the summer months. This is one of the major reasons for the lack of paternal care in the raising of kits, neither mother nor father know which male they belong to4!

In many mustelids, mating is quite rough, involving neck biting and restraint of the female. Pine martens are not known to show such aggression, they are gentle lovers. Mating begins with playful chasing and females do not appear to have neck wounds after mating that are found in other mustelids5,6. However, martens are elusive at the best of times, I am sure there is much we still don’t know.

Gestation

In our last blog ‘Little furry slugs and teenage dirtbags’, we talked about delayed implantation, to find out more about this we recommend you go back there and have a read.

In short, if successfully mated, a females’ egg will be fertilized but the developing cells will not implant in the womb until the following spring, over six months later. So, throughout autumn and winter these females are free to fill up on berries and other autumnal delights then hunker down for winter in peace and quiet. With increasing day length in spring they will seek out maternal den sites and the cycle begins again.

BUT…and this is a big but. Pine martens are not the greatest of breeders.

The long game

Pine martens are not rampant breeders, it is one of the main reasons their recovery has been so slow. Aside from their small litters, females are often not ready to breed until they are nearly three years old. This, in comparison to a weasel who can breed at around three months old1 is practically geriatric. The males also need to be ‘mature’ to some extent and have established a territory. Basically, if he doesn’t have a house and a job, he’s got no chance.

Weasel

Weasel

Adding to the slow start of breeding, many martens will die before they reach two years old. But those that do survive may live for around ten years, this is substantially longer than most other mustelids7. However, this combination of slow breeding commencement, small litter sizes means that every breeding event is vital to the slowly growing marten population.

References

  1. Amstislavsky, S. & Ternovskaya, Y., 2000. Reproduction in mustelids. Animal Reproduction Science 60 pp.571-581.
  2. Ruette, S. et al. 2015. Quantifying the age- and sex-dependent morphological variation in two syntopic mustelids: Martes martes and Martes foina. Mamm Biol 80, 414–423.
  3. Zalewski, A. & Jędrzejewski, W., 2006. Spatial organisation and dynamics of the pine marten Martes martes population in Białowieza Forest (E Poland) compared with other European woodlands. Ecography29(1), pp.31-43
  4. Sandell, M. and Gittleman, J.L., 1989. Carnivore behavior, ecology and evolution.
  5. Birks, J. 2017. Pine Martens. Whittet Books Ltd, Essex, UK.
  6. Enders, R.K., 1952. Reproduction in the mink (Mustela vison). Proceedings of the American Philosophical Society96(6), pp.691-755.
  7. King, C.M., 1980. Population biology of the weasel Mustela nivalis on British game estates. Ecography3(3), pp.160-168.