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Experiment Deelerwoud: evaluatie verzamelde gegevens 2001-2014 ter voorbereiding van het evaluatierapport

Research output: Book/ReportReports of Research Institute for Nature and ForestResearch

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Original languageDutch
PublisherInstituut voor Natuur- en Bosonderzoek
Publication statusPublished - 26-Aug-2015

Publication series

NameRapporten van het Instituut voor Natuur- en Bosonderzoek
No.INBO.R.2015.9092053

Abstract

In 2001 management of red and fallow deer in the Deelerwoud was stopped by Natuurmonumenten. Management of roe deer had already been stopped earlier. This experiment served the purpose of developing an ecosystem that was as complete and natural as possible and in which held opportunities for the development of a natural life style of these animals. Also, the experiment aimed to improve visibility of these animals to the public visiting the reserve.
In order tot evaluate this experiment, INBO was asked to analyse a large number of different available data sources on the different deer populations in the Deelerwoud. However, a number of these data were not sufficiently robust to allow conclusions. The analyses of these data have been carried out as part of this research and are discussed in the report. Since no reliable conclusions could be drawn, none of these analyses were included in this summary.
Changes in numbers and proportions in the populations of large ungulates.
The data show a strong increase in the population size of red deer in the Deelerwoud since the start of the experiment, followed by a stabilisation in the last few years. The observed growth rate was more pronounced than for red deer outside the Deelerwoud and sex ratio stronlgy shifted towards a population that was almost exclusively female. The number of calves per deer doe fell slightly while the general condition of the calves remained stable. The population of fallow deer also increased strongly, but in this case, growth rate was comparable to that of fallow deer populations outside the Deelerwoud and without any stabilisation up to this point. In fallow deer the proportion of females also increased strongly, but less than in red deer and starting from a situation that already held a higher proportion of females. The number of calves per fallow doe decreased strongly over the entire period. The data available on roe deer only allowed to determine that the population has very strongly decrease to extremely low values in het last few years.
Crop damage and deer-vehicle collisions
Crop damage on the ‘Kop van Deelen’ could be attributed nearly exclusively to red and fallow deer from the Deelerwoud. This situation ended with the fencing of this agricultural site, this way reducing crop damage by red and fallow deer to zero. Since the start of the fauna experiment the number of deer-vehicle collisions on the Koningsweg has increased. Especially in the last few years, the number of fallow deer hit by cars on that road was striking. The increase in collisions was directly related to the rise in the population levels of both fallow and red deer in the Deelerwoud, but the number of fallow deer had the most significant effect. The fact that also in roe deer, a species that has experienced a drastic decline in population numbers in the Deelerwoud, a continuous high number of collisions was observed does point out that the relation between collisions and deer densities is clearly species specific. The data also show that, in het large deer species, mainly male animals get hit by cars. This shows that the collision risk is these species is also sex specific, possibly as a result of the difference in dispersion behavior between male and female animals.
Observation chance
The analyses show that the number of observations of both fallow and red deer has significantly risen between 2003 and 2015. The higher chance of observing fallow deer follows the observed population increase for this species. For red deer, this was also the case until 2011, but in this species, the subsequent stagnation of population growth was not reflected in a stabilisation of observation chance. In both red as fallow deer, a decrease in flight distance was observed. In general, the fact that hunting was stopped in the Deelerwoud clearly resulted in positive effects on observation chance of both fallow and red deer, both through an increase in both populations as through a decrease in the shyness of the animals.
8 Experiment Deelerwoud www.inbo.be
General summary
The combined findings mentioned above allow to formulate an answer to the main question and objective of this experiment: does a stop in hunting lead to a more natural behavior in deer species in the Deelerwoud?
In the past, a more intensive terrain use in time and space and a higher diurnal activity were used as typical features of natural behavior. Becaus, in this experiment hunting the only source of disturbance eliminated the general question was only dealt with in function of hunting. Therefore, the changes in numbers and behavior of the different cervid species in the Deelerwoud were compared tot what could be expected of cervid populations that are not (or almost not) hunted.
 The first expectation when hunting is stopped under conditions without major predators is a rise in population numbers until a new stable state is attained. In this case, growth rates are expected to be higher than those in comparable populations. For red deer in the Deelerwoud this was the case. For fallow deer, who also experienced a significant population increase, population growth rate was not higher than in populations in adjacent areas, but densities in the Deelerwoud were much higher. In addition, a 10 year term is described as the normal time it takes red deer to attain a new stable state after hunting has ceased. In the Deelerwoud population growth has indeed stabilised after 10 years. In fallow deer, even after a period of 13 years, no such stabilisation was observed.
 The increase in the proportion of females in both red and fallow deer is in line with observations in other studies on non-hunted cervids. Also, the observed decline in the number of calves per doe in high density populations of both red and fallow deer fit the expected pattern. Finally, low hunting pressure has been shown to lead to higher group sizes in red deer, a trend also observed in the Deelerwoud population.
 Population growth and composition thus both match the expected pattern for a hunting stop in a setting without predators and in which food is abundant. For fallow deer, the situation in the Deelerwoud differs from that of red deer in the sense that population size has not stabilised yet. The increase in the numbers of both fallow and red deer have led to a decline in roe deer numbers through interspecific competition. This way, the roe deer decline in the Deelerwoud is an indirect result of the hunting stop.
 The reduced shyness in red deer is probably als the result of the hunting stop. For fallow deer, this was not observed, but flight distance in this species was very low from the early stages of te experiment on. In general, the behavior in large cervids in the Deelerwoud matches the expectations for populations with very low or no hunting pressure.
In conclusion, both red and fallow deer clearly show the effects of the hunting stop in the Deelerwoud. In population growth, composition as well as in behavior, both species show strong parallels to observations made in other non-hunted populations. For roe deer, these effects are secundary and are probably the result of the increase in the fallow and red deer populations.
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