Research and Methodology
On this page you can read about our different research topics and how our research is conducted.
2) Monitoring of bears
a) Radio transmitters
c) Implant – intraperitoneal radio transmitters
a) Immobilization Update 2008
4) Which bears are captured and marked?
5) Information from shot bears
Our primary method is to follow individual female bears and their female offspring from birth to death, thus creating pedigrees, many of which now cover five generations. Since the project started in 1984, our research has expanded and new techniques, such as genetics and GPS telemetry, are giving us the possibility to answer new and important questions.
Presently, our basic research is concentrated on understanding the following:
- the social organization of female and male bears, including chemical communication
- the mating system, including the role of MHC (major histocompatibility complex) in mate choice and the role of sexually selected infanticide
- life history strategies (growth and reproduction)
- population ecology, including the individuals’ contribution to population growth
- genetics, including spatial genetic relationships and heritability of traits
- general physiology, including cooperation with researchers working on human physiology questions.
Our more applied research questions often give us answers to basic questions as well. Our present applied research is concentrated on
- the demographic and evolutionary effects of hunting harvest on bear populations
- estimating the size and trends of bear populations
- the effects of human presence on bear behavior and habitat use
- the brown bear as a danger to humans
- the short- and long-term effects of capture and marking of bears
- the effects of use of baiting on bear harvest
- the direct and indirect negative effects of bears on free-ranging livestock.
- bears as a predator on semi-domestic reindeer
2) Monitoring of bears
The bear is a shy animal that moves over extensive areas. To monitor them we equip them with radio transmitters or GPS-receivers. Until 2003 we used only the traditional VHF technology (i.e. radio transmitters). Since then we have replaced more and more of those with GPS-collars.
The bears that still have regular radio transmitters are currently located one to two times per month during the non-denning season. This low level of monitoring is sufficient to continue the long-term demographic study of the population. It gives us a rough idea of their use of area, documentation of their dispersal, and we can also locate a bear and determine the reason for its death. Mainly female bears are included in this study and we mark their yearlings in the spring, before they have separated from their mother. Thus we can keep track of bears and their kinship through generations. We study the survival of cubs and the time of separation by tracking the radio-marked females with a helicopter to observe them and count their cubs. We count cubs three times per year; 1) in spring after they have left the den, 2) in summer following the mating season, and 3) in fall before they enter the den.
The bears with GPS-collars give us a whole different flow of data, compared to those with radio transmitters. As a standard we have programmed the GPS-receiver to take a position every 30 minutes during spring, summer and fall, and one position per day during winter, while the bears are in the den. The GPS-positioning schedule can be reprogrammed for a more or less frequent positioning, depending on which study the bear is included in. Very frequent and exact positioning enables us to more precisely and on smaller scales than before study aspects of bears’ biology, such as their movements through the landscape, behavior, predation and habitat selection. By having many bears equipped with GPS-collars simultaneously in the same area, we can also study the interactions among bears and how they are effected by gender, kinship, and season.
2a) Radio transmitters
With a receiver that picks up VHF radio signals, we manually localize (radio-track) bears with radio transmitters from a distance. By triangulating directions of the signal, we estimate the position of the animal (generally within a few hundred meters accuracy). To receive the transmitter signal from ground, we must be within a few kilometers, or sometimes a few hundred meters, from the bear, depending on terrain. We mainly radio-track from cars, though depending on study and area, we may also radio-track from an airplane. As bears move over extensive areas, it requires a high investment of time and fuel to manually radio-track them. When tracking from a car, the search is restricted to areas with roads and quite often bears are not found. In addition, manual tracking is often restricted to day-time hours and/or certain seasons. Hence one gets a limited amount of positions per each bear during confined periods. The benefits with the traditional radio transmitters are that they are uncomplicated, robust, have a long life span (the battery lasts 4-5 years), and they are relatively cheap.
GPS (Global Positioning System) is a satellite navigation system. By receiving signals from satellites, the GPS receiver calculates its position in longitude, latitude and elevation. The GPS technology has in many aspects revolutionized wildlife research. The GPS-receiver on the animal can take positions very accurately and frequently, without restrictions to specific periods. Hence one will get a very precise picture of the animal’s movements independently of time of day and area. However, each positioning requires battery power, making the positioning frequency a trade-off between how often one needs positions for the study and how long one needs to collect data from that bear. The disadvantage of GPS-collars is that they are technically complicated and not as robust as the radio-collars, and they are very expensive.
In this project we use GPS-collars that, apart from a GPS receiver, also have a GSM-module, radio transmitter, and an activity sensor. All position and activity data are saved in the GPS, and the GSM module sends the latest positons as an sms to a receiving station. The researchers can access all the data by linking to a database that is connected to the receiving station. The radio transmitter is only turned on when we need to track the bear manually. The activity sensor measures the bear’s movements in X and Y axis, and can give us a rough estimation of the bear’s level of activity.
In our Northern study area the GSM coverage is very limited. There, instead of GPS/GSM, we use GPS/Iridium collars that send the bear’s latest positions via satellites to the receiving station.
2c) Implant – intraperitoneal radio transmitters
Currently subadult bears and bears with GPS-collars receive a radio transmitter that is surgically implanted into their peritoneal cavity, a so-called implant. The reason for equipping subadult bears with implants is to avoid capturing them every year while they are still growing, which is necessary if they receive a radio-collar. Bears with GPS collars receive an implant as a back-up to find them again, should their GPS-receiver fail. As the GPS-receivers continue to be improved, we hope that soon it will not be necessary for us to use an implant as a back-up.
Studies made within this project have shown that, in some cases, the implants needs to be replaced after 5-6 years, which also is the extent of the battery capacity. Nowadays our routine is to remove the implants after 3-5 years.
To mark and collar bears, we must capture and immobilize them. Bears are captured from a helicopter by an experienced team using a remote drug delivery system (Dan-Inject). Most captures are made in spring, shortly after bears have emerged from their dens. Spring provides the best conditions, when remaining snow cover and minimal vegetation make it easier to find the bear, open water in the terrain is limited, and ambient temperature is relatively low. While the bear is immobilized, we either put on, take off, or replace its technical equipment. We record a number of health status parameters and take samples for genetic and other studies. From bears of unknown age, we pull a tooth (a premolar without function for the bear) for age determination. Additionally we weigh the bear and take a number of body measurements. When a bear is captured for the first time, we give it a coded ID number, attach an eartag, inject a microchip into the skin and tattoo its ID number inside the lip. Together with the DNA information, this ID-marking is important to ensure a secure identification of the bear next time it is encountered.
The document "Biomedical Protocols for Free-ranging Brown Bears, Gray Wolves, Wolverines and Lynx, 2007" describes the procedures of capture, immobilization and radio-marking in detail.
3a) Immobilization Update 2008
Since the project started in 1984, bears have been captured yearly. Until and including 2008, a total of 1431 captures have been made of 603 individual bears. Of these 405, have been radio-tagged. The number of captures exceeds the number of individuals because many bears have been captured several times. A radio-tagged bear is generally captured at two-three year intervals to replace its transmitter/receiver. Each year we loose contact with some of our marked bears. Most of them have been shot during the bear hunt, others are lost to us because their collar has fallen off. Also, it is not uncommon that younger bears are killed by older, more dominant bears. Most of the knowledge about bears that the project has acquired is based on the data from the 1414 bear-years that we have monitored individual bears. (One bear-year means that an individual has been monitored for a full year, or that 2 bears have been monitored for half a year each, etc). During 2008, a total of 91 bears were followed until they entered their dens.
4) Which bears are captured and marked?
Adult radio-tagged bears are captured when their transmitter or receiver needs to be replaced. Females with cubs of the year are not captured. The bear can carry a regular VHF radio-collar for 3-4 years before the batteries run low and the collar must be replaced. How soon a GPS-collar needs replacing depends mainly on the number of positions it has taken. Generally GPS-collars are replaced every 1-3 years. As the GPS-collars are technically complex and not as robust as radio-collars, we often have to replace them sooner if they stop functioning. Young bears that have been equipped with collars must be captured each year while they are still growing to receive a larger collar.
The collar belts are fitted with a break-away zone, a strap of cotton fabric, that rots and weakens over time. This ensures that the collar will eventually fall off the bear, should we loose contact with it.
During the spring, we capture the entire family of a radio-tagged female with yearlings. The female yearlings are equipped with a transmitter (since 1998 these young bears have also received an implant, see above), so we can continue to follow them. The male yearlings are only ID marked with an eartag, ID tattoo, and microchip. Thus, even marked male bears can be identified later if they are found, for example if they are shot during the bear hunt or if we capture them later as adult bears.
5) Information from shot bears
Another important part of our research is to collect information on bears that have been killed during hunting. We obtain information on weight, a tooth for age determination, skin, hair, and tissue samples, the reproductive organs, killing site and killing date, method of hunting and information about whether the bear was marked and/or tattooed inside the lip. This gives us data from bears both inside and outside our study areas, from bears the we have only ID-marked, and from bears we have lost contact with. Extensive genetic studies have been made based on hair and tissues from both killed and marked bears. The information the hunters provide about the hunt is valuable data for studies of the effects hunting has on the bear population.