Monitoring Gray Rat Snake Nest Boxes

Ruthven Park supports Gray Ratsnake recovery strategies by providing nesting locations, winter hibernacula, and old growth forest conditions. Gray Ratsnake are a tree-dwelling snake, and as Ontario’s largest snake, they have large ranges and their survival depends on larger extents of forest-rich natural areas.

Gray Ratsnakes are near their northern extent in the Carolinian zone of the north shore of Lake Erie (Carolinian population). One other population exists further north near the outlet of Lake Ontario (Frontenac Axis population).  To date Gray Ratsnakes have not been detected on Ruthven property, but they are present on lands adjacent to the property, and Ruthven is proud to continue to mange the Land Trust property to build greater extents of forest-rich habitat on the landscape for this and other forest dependent species that are rare in Ontario.

Snake Habitat at Ruthven Park

Ruthven Park features a mosaic of deciduous forest, wetland, and open habitats used by Gray Ratsnake. During warm months of the year Gray Ratsnakes forage, mate and nest in or near woodlands in the rural landscape. Gray Ratsnakes nest in warm, composted material such as the interior of old decaying snags, logs and stumps. Large decaying logs and stumps are uncommon in the forests at Ruthven due to past logging activities, but today the forest is managed to include old growth trees, and dead wood is allowed to decay in situ to eventually provide naturally occurring decaying snags (standing dead), stumps and logs for snake nesting habitat, and many other forest functions.

What more critically defines their use on the landscape is natural or cultural features that are suitable during the cold winter months when snakes hibernate under ground. Winter hibernation areas allow snakes to get below the frost level, and provide suitable oxygen and moisture to maintain the needs of the snake over the 6-month underground season.  On the Haldimand Clay Plain, hibernation areas are often part of naturally occurring rocky outcrops of bedrock, or holes, caves and sink holes in valleys and woods, but include cultural features such as unused buildings and old foundations. These types of suitable winter habitat occur on the Ruthven property, and though natural hibernacula have not yet been identified, 2 constructed hibernacula (2014), and some building foundations are monitored for signs of snake activity in spring and fall.

Nest Boxes

In order to supplement nesting habitat opportunities (more quickly than waiting for the forest to decay) Gray Rat snake nesting boxes were established on Ruthven property in a joint project with Haldimand Stewardship Council, Ministry of Natural Resources & Forestry and the Land Trust (2010). Additional boxes were constructed by the Land Trust and local landowners as part of a public Gray Ratsnake Earth Day Event in the spring of 2014. The Land Trust currently maintains and monitors 9 nest boxes at Ruthven, and continues to run educational workshops to build more boxes.  The Leeds Grenville Stewardship Council, who works with the Frontenac population of Gray Ratsnake, lends valuable advice and data sharing for our project.

Nest Box Construction & Placement

Nest boxes are intended to mimic natural nesting conditions in warm composted material, as well as provide protection from egg-eating predators! The boxes are a bottomless 4’ cube made of a light wooden frame and enclosed by galvanized wire. The wire has 2”gaps; wide enough for small mammals and snakes to access, but too small for predators such as racoons or red foxes to damage or consume eggs or new-born snakes.

Locations at Ruthven are within or adjacent to forests, keeping in mind the need for solar input to generate composting activity and appropriate heat to incubate the eggs. Nest box locations across the property target areas that are:

  • rich in rodent use (open habitat)
  • have good sun exposure (high solar input into nest box material)
  • are out of the prevailing winds (to contribute to high nest box temperature),
  • near or within area with vertical escapes (forest), and
  • have enough moisture to stimulate composting (near roof or tree driplines).

Boxes are filled with a mix of straw and fresh wood shavings/chips, and leaves collected from the native forest from around each box. Boxes are typically filled in fall, and topped up in spring before the nesting season starts in late spring / early summer. Remember, this snake is up to 1.9m long, so a 4’ cube nest box is enough room, if it is full!

Boxes are left untouched from spring till fall and assessed in later fall, following the hatch and dispersal of the year’s young. All contents are examined in the fall by hand for snake sheds or eggs, and rodent activity. Boxes are repaired as necessary and then re-filled with the old compost material and fresh material.

In 2016 the boxes were filled with the previous years’ composted material and then topped up to full with 2 large garbage cans worth of wood chips and 8-10 large cans of leaves. Pieces of locally collected rotten wood were incorporated into the mix to increase roughness of the nest material, create holes and niches. The boxes will now be left for winter, and in spring, before the nesting season, each box will be topped up with new materials (largely straw and wood chips, which are available).

Cathy Blott, Landscape Biologist Consultant

Nest Boxes 1 & 2 along crest of the east bank of the Grand River in mature maple / oak woods
Box 4 in meadow habitat adjacent to hedgerow tree features and Rogers Creek Box 5 in meadow habitat adjacent to ~5acre forest & hedgerow trees
Setting of Nest Boxes 6 & 8 in successional meadow ‘inlet’ in surrounding deciduous woods Box 6 – Inner core of old material well composted & moist.
Nest Box 6 example of bottom layer of old material with rotten woody material incorporated into mix. Filling rest of the box with local wood chips and leaves.
Nest Box 7 nestled in back corner of large field againt forest, with a south facing aspect Nest Box 7 Small mammal nest found in bottom central portion of old material.
Nest Box 3 & 5 examining old material with dense layer of snails at bottom center. Nest Box 5 close up showing density of snails.