California Department of Fish and Wildlife

Featured Scientist

Tim Kroeker
Tim Kroeker drawing blood from a tranquilized deer

Tim Kroeker

Tim Kroeker is an environmental scientist for the California Department of Fish and Wildlife’s Wildlife Branch. He started with the Department in 1987 as a scientific aid. He later worked for the Pacific Southwest Research Station as a wildlife biologist before returning to the Department about three years later as an environmental scientist. His current position covers a large geographical area with primary responsibility for Madera and Mariposa counties, but he regularly assists with projects in six other counties, two national forests and a national park as well as federal lands owned by the Bureau of Land Management, the Bureau of Reclamation and the Army Corps of Engineers. He holds a Bachelor’s degree in Environmental Biology from California State University, Fresno.

What are your primary roles within the Department?

A lot of the job is public interaction with hunters, landowners and other outdoor enthusiasts. I regularly field calls for trapped wildlife. Wildlife rescues can be anything from a red-tailed hawk which landed in a field of cockle burrs and had so many burrs that it was rendered flightless until I removed them, to a bear that put its head into a milk can and got it stuck. The milk can incident was one of my first and most memorable rescues. The can was one of those old fashioned galvanized milk cans that people use for decoration. It probably weighed 30 pounds and by the time I got to the bear, he was so tired from stumbling around with it on his head that I just walked up and gave him an injection of tranquilizer drugs. It took so long to get the can off his head that he was waking up by the time I was done.

I also respond to nuisance wildlife calls, which can involve bears, pigs or turkeys that are causing property damage or are a public safety threat. In some cases, I issue depredation permits but usually after investigating and talking through the incident, I can make suggestions to resolve the problem without harming the wildlife.

I have a lot of other public interaction on other levels too. For instance, I provide support for hunter check stations during hunting season. The main purpose of the check station is gathering valuable information related to the health and age class of harvested animals. It’s a great opportunity to collect biological samples. These check stations are highly visible and we have the opportunity to talk to many people from the general public as well as the hunters. We answer a wide variety of questions related to wildlife as well as check tags and licenses and verify paperwork.

My duties also include conducting wildlife surveys on game animals like deer and doves as well as for specific species of interest (such as the endangered San Joaquin kit fox). I write reports on my findings and provide information and education to the public.

What current research are you doing and what is the significance?

The biggest project I have right now is a telemetry research project for the Upper San Joaquin River Watershed. We have radio collars on deer and are tracking migration, survival, habitat use and how the migratory deer interact with non-migratory deer. Some of the collars we have now use satellites to transmit the deer’s location to my email. So this is real breakthrough technology – we know where a deer is within a few yards in real time, almost daily. If the deer dies, we can get on site a lot quicker to determine cause of death. Historically we have had to rely on positions taken from aircraft on a monthly basis and the locations were only within a mile or so. Aerial monitoring is very expensive, so now we get better quality and more data at a lower cost. When we capture deer, we also get a lot of wildlife health information from the blood, hair and parasite samples. We are learning a lot about the spread of a non-native louse that has really devastated fawn survival in some areas.

I do a lot of population survey work for deer management, which involves winter and spring composition counts to get an idea of fawn survival and population stability. We do the same for other species. In the case of doves, I participate in a nationwide mourning dove coo count survey, which involves a driven transect with listening points. During the same time frame other biologists in California and across the United States are doing the same thing.

What are some of the interesting things that you have run across in your job?

Almost every time I get into the field something interesting happens at some level. One of the most exciting things happened on a routine deer survey. We observed a great gray owl, which is a California endangered species. A few days later that owl observation led us to a nest site at the far south of their documented range. Later that spring I was able to document success when the young owls fledged.

What are some of the biggest threats to California’s wildlife?

From my perspective, the biggest threat is habitat change. If you look at photos from a hundred years ago, forest and woodlands were a lot more open. A lot of the plants we take for granted are actually naturalized transplants from Europe. Invasive exotic species including plants like salt cedar and animals like feral pigs are having a dramatic negative effect on native plants and animals. Urban sprawl, hydroelectric plants, solar and wind projects have all put a strain on our wildlife habitat. Climate change could become a major factor too. Although there has been a lot of research, there is a lot more that we don’t know.

How did you become interested in wildlife?

I was always interested in wildlife, from as early as I remember. I liked watching wildlife shows on TV, reading wildlife books and drawing wildlife. My grandfather had a farm in the Merced area and there was always a lot of wildlife there. It was a typical small farm from a bygone era; bygone even by the standards of 40 years ago. He mostly grazed cattle and never farmed to the edge of his fields. He flood irrigated and there was just a lot of cover and wildlife there. My brothers and I could roam all over the place and as we grew older started hunting there. So it was just a case of growing up interested and around wildlife.