Possums are the prime suspects behind the bark damage that has killed numerous fivefinger trees on a Coromandel property.
When Annette Steele and Ben Hunter returned home last spring after some months away they noticed the trees had been extensively ringbarked. Some were already dead. The others, already stressed by the damage, died during the dry summer that followed.
Annette referred to Pest Detective to help identify the bark munchers. The long, straight scrape marks with a darker line down the middle pointed to possums, rabbits or hares. All three species make such marks with their front incisor teeth.
However, rabbits and hares were ruled out because the damage was too high (extending up to more than a metre above ground). The shady forest interior was also not typical rabbit and hare habitat.
The bite marks were consistent with those of possum in both size (4.5 – 7 mm width across both teeth) and the thin dark stripe in the middle. This stripe of slightly upstanding bark is left by the gap possums have between their front teeth. The diagonal / horizontal alignment of the bite marks also pointed to possums, as other animals who damage bark are more likely to leave vertical marks. Goats, for instance, which Annette says have occasionally damaged tree bark, tend to pull strips off vertically rather than gouging with their teeth.
Strangely, the only affected tree species was fivefinger (Pseudopanax arboreus). No similar damage was evident on other types of tree, including the closely related coastal fivefinger (Pseudopanax lessonii) which was also planted extensively on the property. Possums are known to like eating the leaves and fruit of five finger but why they focused on the bark and the one species remains a mystery.
Annette and Ben will be upping their possum control to protect the hard-won native vegetation on their 10-ha block of former farmland, which they bought four years ago.
“We fell in love with this place,” Annette recalls. “The previous owner had transformed it with extensive planting of locally indigenous species over a 15-20 year period and achieved a closed canopy over most of it. We do get other pest animals, and use a combination of DOC 2000 trapping, possum bait stations and Timms or leghold traps for possum pelts. Unfortunately, the possums just keep coming!”