Saturday, July 11, 2009

Protecting Wildlife While Mowing

--- Nest of baby bunnies found by Miriam Sachs Martin while moving tarps. ---

We mow to control weeds and to reduce fire hazards around our home and ranch buildings. But the mowed fields can also be the home of wildlife, so how do you protect wildlife while mowing? Animals that may be harmed while mowing, weed-whipping, brushcutting or discing grasslands or weed stands are: ground-nesting birds, snakes, frogs, toads, turtles, lizards, salamanders, rodents, and rabbits. Even small fawns may be hiding in the grass, and if they are following their mama's orders, they won't budge until she says so. If you want to keep the wildlife while modifying the plant environment, here are some tips to consider while mowing.

PRE-CHECK - Walk the line, walk the field. It's a good idea to start by walking across your work area to remove mowing hazards such as rocks, branches, and badminton rackets anyway. This is also the time to check for wildlife and develop a response plan. Inspect your work area before you turn on the equipment - noisy engines scare some animals into hunkering down and hiding in place.

--- Southern alligator lizards are especially slow, perhaps it's that long tail. ---

When mowing long, straight lines with a big tractors such as for a fire break along a road, some folks have one person walk in front of the tractor during the whole mowing operation to flush any wildlife. For larger fields, you don't have to walk the entire area - just crossing the area several times may flush visiting critters away. You can keep the snakes and lizards rolling along by walking behind them until they are well outside the work area and unlikely to turn around and come back. Turtles may appreciate a lift. Fossorial animals (= digging) may dash into a burrow and stay there until the commotion is over.

California quails, grasshopper sparrows, and western meadowlarks are common birds that could be nesting on the ground and are easy to flush. Detecting and avoiding their eggs or nestlings can be more difficult. Look for birds singing repeatedly at the same location to claim territory around their nests. If you notice birds that flush from the ground, act defensively, feign broken wings or fly into the grass with nesting material or food, it is likely a nest is present. Some adult birds chirp repeatedly as you approach a nest. High pitched calls may be nestlings. Careful, quiet observation may help you discern where the birds are flying in and out of the vegetation and where the nest is generally located. Some birds pull strands of surrounding grass over the top of their nests as camouflage; train yourself to look for patterns of bent-over grass as possible nest locations. Stay about 15 feet away from the probable nest location and treat the weeds with less disruptive methods (spot spraying of herbicides or handpulling), or mow this area later in the season, if possible. Remember that many birds nest more than one time in the summer.

TIMING - Mow early or late, or carefully in between, and know your grassland critters and when they might be seen.

One way to avoid striking wildlife with your mowing implement is to delay mowing until after midsummer when nesting is done or slowing down. Unfortunately, you may not be able to wait since this is often too late if you want to prevent annual weeds from going to seed. Furthermore, annual grasses should be mowed while they are still green to prevent hot mowing equipment from igniting a fire in dry, brown grass. Another precaution in fire hazard areas is to mow before 10 AM during the summer when moisture of vegetation is higher and less likely to ignite. See the mowing, string trimmer and other short videos at the CAL FIRE website for excellent safety tips on mowing during the fire season.

You can also adjust your timing by the weather or time of day. Animals are less likely to be moving about in the grass on a cool or an especially hot day, but those that are resting in the grass are slower to retreat, so be especially alert. The same holds true for the cool and hot parts of the day. Reptiles and amphibians use the sun to modify their body temperature, so you are less likely to come across them in the morning, however, carefully check sunny spots on a cool morning where reptiles may be warming up for the day. Birds are happy and singing in the morning, so that is a good time to precheck for them.

--- Gopher snake in the grass. ---

MOWING PATTERNS - Mow outwards and pause at edges. Circling inwards is a common mowing pattern in urban yards, however, in fields, this may force wildlife to retreat into the shrinking patch of tall grass in the center where they are most susceptible to being hit as you finish up. You can change your mowing pattern so that you are mowing inside-out or in consecutive rows rather than circling inwards. See mowing diagrams of inside-out and consecutive rows at this Indiana Division of Fish and Wildlife website.

For mowing inside-out, make the first cuts through the middle of the work area and progressively circle towards the outside edges. This allows wildlife to move outwards away from the noise and cutting blades. This requires a tight turning radius for the first few passes so that you may need to reverse and forward large-wheeled equipment several times on the first few turns. You will also be initially throwing cut material onto your second mowing pathway.

Mowing in consecutive rows can "push" the wildlife to the edges of the mowed area. It requires a tight radius at every turn, so is more appropriate for unwheeled equipment like string trimmers and brushcutters.

Consider leaving edges along fences and rocky areas to last when you are mowing. This not only leaves these areas as retreat and hiding places for animals, but because rocks and fences are the locations where you are most likely to ding and dull your cutting blades or strings, you have less maintenance if you end the mowing session there. Some people will mow part of a field one day and leave interior or edge areas for mowing a few days later to allow wildlife to move out.

On very large fields, another strategy is to cut one-third of the field each year and leave the rest to wildlife, if that meets your other mowing goals. In general, leaving some uncut areas on the property will benefit wildlife.

EQUIPMENT TYPES & MODIFICATIONS - Mow up, look down. For equipment that allows adjustment of the mowing deck, set the mowing height 4 or more inches above the ground, if that otherwise meets your mowing goals. Mowing several inches above the ground may avoid nests and small animals, and I find this works fine to stop mustard plants that have started to flower. However, mowing several inches high may not sufficiently set back some weeds like thistles which will resprout and seed, and thus require subsequent summer cutting and another round of potential disturbance.

Brushcutters and string trimmers allow the operator greater visibility and quicker response time if wildlife is observed while mowing. They also allow greater flexibility in momentarily adjusting height and the direction of the cutting path and are faster to turn off. Operators tend to cut more slowly when using these unwheeled cutting implements, thus they give wildlife a longer time to escape the commotion. These hand-carried implements can be more time consuming and tedious to operate over large areas. They are better for small areas or to trim out edges or especially sensitive areas near water or brush. Invest in a good harness for brushcutters. Your comfort will allow you to have greater maneuverability and cover more area in potential wildlife habitat before you fatigue.

--- Joe Mackessy uses a brushcutter with a harness and bicycle handles
that give him greater control and comfort so he can work carefully and longer.

Wheeled mowers and tractor-pulled brushogs are less flexible in turning, but they can be raised to a regular higher cut. These large mowers can be modified with flushing bars or leading edges on the decks to flush wildlife in front of the equipment or prevent small animals from being sucked in under the deck. Slow down the pace of these larger pieces of wheeled equipment to give wildlife time to escape.

EXPERIENCE - I like to compare mowing to food preparation. With time, you accumulate more and better quality cutting tools and are able to match the right tool for the right job. You also become more aware of avoiding living things (like your fingers or bunnies). Neighbors who share recipes may also have good tips on mowing.

It is difficult to mow in the spring and summer in the country, meet your weed control and fire safety goals, and completely avoid wildlife. These tips should help you thoughtfully seek ways to lessen the possible conflicts. The most important tip is to SLOW DOWN - it gives you time to observe, gives wildlife time to retreat, and as always, be safe.

The safe mowing chant:
  • Walk the line, walk the field.
  • Mow early or late, or carefully in between, and know your grassland critters and when they might be seen.
  • Mow outwards and pause at edges.
  • Mow up, look down.
  • Slow down.
Thanks to Heather, Miriam, Stan and others for their advice on this topic. If you have any other suggestions, especially innovative mowing patterns, please comment on this posting.



  1. Can you put a 'share' button on your blog? I would really like to send this to a couple facebook friends. In the meantime, I'll copy and paste the link.



  2. PS - not only are alligator lizards slow, but females will stay and protect their young, even in the face of a weed whip!

  3. Miri: I added an option at the end of each post that allows you to email the link to friends. See the little envelope at the bottom of each posting. Is that what you meant? -C

  4. Re-reading this excellent post several years later, from the new perspective of hiring contractors to mow large swaths. The fine art of managing mowing is an ever-moving target (so to speak). If the mower blades are high before the Spring rains stop, won't some annual grasses have enough juice to re-grow a seed head?


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