Dr Roger Lambert
School of Biological Sciences, University of Aberdeen
There are two subspecies of roe deer: European, Capreolus capreolus and Siberian C.pygargus. There is a degree of uncertainty by palaeontologists as to the origins of the roe deer, but it is believed that the earliest roe fossils are placed within the stem-genus Procapreolus. These fossils, which were found in the Ukraine, are from the Middle Miocene period (approximately 10 million years ago).
The European roe deer and Siberian roe deer lineages are known, through DNA analysis, to have separated about 2-3 million years ago. This suggests that the European roe deer is a truly ancient species having evolved little in the last million years.
European roe deer range from north of the Arctic Circle to as far south as Iran. They occur in all European countries except Iceland and Ireland.
The roe deer rut tales place at the end of July and beginning of August each year. The female roe deer is monoestrus, which means she has a single annual sexual cycle. All other species of deer are polyoestrus and have several sexual cycles, which usually start in the autumn. Also, in most other species of deer, females are pregnant for about seven months; a female roe's pregnancy lasts for 10 months, and the kids are born between mid May and early June of the following year.
The European roe deer is the only artiodactyl (even-toed hoofed mammal) to exhibit the phenomenon of delayed implantation (biologically known as embryonic diapause). After the egg is released from the ovary in the female and fertilised by the sperm from the buck, it travels to the uterus and remains for five months unattached ‘floating’ within the uterus. During this time the cells of the embryo divide and multiply very slowly. Unlike those of other species (including those with delayed implantation), the un-implanted embryo controls its own growth in the uterus. At the end of December or early January, when the embryo is little more than 0.3mm long, it is genetically programmed to reactivate from the period of delayed implantation. The embryo sends a message to the mother in the form of a protein unique to the roe deer. When the mother receives this message she starts a ‘cascade’ effect of hormones (mostly oestrogens), which enables the embryo to rapidly expand. After a short period of very fast growth, the embryo attaches to the inner wall of the uterus, forming a link with the mother through the placenta, and normal fetal growth follows for a further five months.
Delayed implantation is a very successful strategy for roe deer. In late July, when mating takes place, does are in peak body condition as a result of a plentiful supply of food and are, therefore, at they’re most fertile. Does continue to gain reserves during the autumn while the ‘floating’ embryo or embryos – roe deer usually have twins and sometimes triplets – are making very little demands on her. She then has sufficient reserves to see her through winter, when food is scarcer and of poorer nutritional value. When the kids are eventually born in late May, the climate is favourable giving them a better chance of survival.
For information about roe deer giving birth go to Giving Birth
To learn more about the European Roe Deer try these links:
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