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Building a hibernaculum

Hibernaculum for reptiles and amphibians

A purpose-built garden hibernacula

Image: John Day

DIY enthusiasts might consider building a hibernaculum to provide an additional safe haven for amphibians and reptiles. You can also provide additional accommodation for solitary bees and wasps.

Hibernacula for amphibians

Amphibians require a little more humidity, and hibernacula for them are best located nearer to water. A well-drained rockery near a pond is ideal. You could even use soil dug out from creating a pond for it.

You will need plenty of coarse rubble mixed with plenty of leaf mould and coarse pieces of wood. This needs to be placed where you will be putting the spoil from your pond.

  • As you dig your pond, add plenty of rubble, and wood with the soil as you cover the brick rubble base. Cover the edges of the bricks with paving slabs or large pieces of concrete to create gaps that allow amphibians into the mound. Cover these in a thin layer of soil and brash, taking care not block any gaps off. 
  • If you are not using spoil from a pond, first dig a hole 45 cm deep (1.5 feet). The area will be dependant on the space you have available, but a minimum of two square metres (6 square feet) is ideal. To complete the hibernaculum, follow the instructions described above.

Hibernacula for reptiles

  • Orientate the hibernacula on an east-west axis, so that one side is south facing.
  • Dig a trench between 600 and 900 mm deep (2 ft to 3 ft) and 1.5 to 3 m long (5 ft to 10 ft). Place a section of 100 mm to 150 mm (4 ins to 6 ins) diameter plastic pipe with plenty of drainage holes drilled into it in the hole.
  • Cover this with coarse rubble to the level of the trench and use 20 mm (0.75 in) shingle to top the rubble and loosely fill any gaps. Place some old logs at right angles across the trench.
  • Place some short lengths of 50 mm (2 ins) waste pipe along each side of the trench at an angle of approximately 30 to 45 degrees. Depending on the length of trench, space them at approximately 300 mm to 450 mm (1 ft to 1.5 ft) intervals. These help give the reptiles access to the chambers below, although where possible they will burrow in through the soil-rubble mix.
  • Cover the trench with a mix of soil and rubble, ensuring the waste pipes protrude just above the finished surface, which should resemble something similar to a long barrow. Cover the top with a layer of rubble or better still, shale from a local quarry.

Important information

  • Hibernacula must be free-draining. Avoid digging a straight-sided pit into clay.
  • Plant or allow vegetation to grow naturally on the north side of the mound for extra shelter.
  • Plant plants and low growing shrubs whose flowers attract insects.
  • Prevent vegetation from encroaching onto the south facing side of the mound. Periodic thinning also helps prevent a thick root matt developing, making it hard for reptiles and insects to burrow into the surface.
  • Maintain sparse vegetation cover on the south facing side to give the animals somewhere to bask. It also provides basking space for insects and for solitary bees and wasps to nest. It may also provide a place for house sparrows to dust bathe in and feed on insects and seeds.