We need to talk about ivy

Since 2007, bat survey guidelines have listed ivy as a feature used by tree-roosting bats. Despite this, very few records of bats roosting in ivy exist. With a lack of evidence, is it justified to continuing to survey ivy for bats? 

Origins

As part of his research for the Bat Tree Habitat Key, Henry Andrews undertook a comprehensive desk study into bat’s use of ivy. This is what he found.

Not much, but back in 2011 we knew very little about bats in trees.  

The Bat Tree Habitat Key 

This project developed a common language and survey method for bats and trees. Between 2011 and 2020, four editions of the key were published. This lead to an increased knowledge of tree-roosting bats and a huge number of records – the database contains details of over 1000 tree roosts. Despite considerable effort, just two new accounts of bats using trees covered by ivy were added to the list. 

As well as the low number of records, it’s also interesting that not a single photo of a bat roosting behind ivy exists – we have them for all of the other Potential Roost Features.  

It’s no wonder that the Bat Tree Habitat Key concludes: “Ivy is not a regularly used roost feature and the probability is that the greater proportion of bat species make no use of it whatsoever.”

Records not shared to the Bat Tree Habitat Key

A search for the word ivy on UK Bat Workers Facebook group returns two posts with records of bats using trees covered by ivy:

Here are links to the posts listed above – Colleen Hope & Iain McBatt – (they will only work if you are a member of the group). 

What about in Europe?

During a systematic literature review undertaken for barbastelle and Bechstein’s bats, no European studies have documented bats roosting behind ivy.

I even asked chat GPT to help – it didn’t return any results from primary research. 

Clearly justified?

Government guidance on the Natural Environment says:

“As with other supporting information, local planning authorities should require ecological surveys only where clearly justified.”

If you accept all of the above records, we have just 11 trees where bats have been recorded in trees covered by ivy. Considering the millions of trees covered by ivy in the UK – is that enough to justify survey?

To put it another way, bats turn up in unusual places all the time. Here are some examples from the UK Bat Workers Facebook group.

Links – Louis Pearson, Grace Dooley, George Aridgway & Gail Armstrong – (they will only work if you are a member of the group). 

Based on that evidence, should we be recommending the survey of garden parasols? 

Ivy obscuring Potential Roost Features

What about behind the ivy? I hear you cry! There could be hidden features. 

To this I say two things:

1. Ground Level Tree Assessments are by their very nature, constrained: You are on the ground and trees are tall, it is unlikely to be able to see 100% of the tree surface e.g. top of branches. Does that mean we climb every tree to check, just in case? No, that would be unreasonable. We have to base our assessment on what we can see. If a feature is visible – then follow up. If not, then the survey is concluded.
2. The courts have ruled on the topic of ivy covering trees; The case* relates to tree risk management and acknowledges that whilst ivy may obscure obvious defects, it would be disproportionate to remove ivy on all trees. Only where a ground level inspection identifies a feature, would further action be required. Therefore, the presence of ivy alone does not require further action.

*Stagecoach South Western Trains Ltd v Hind & Steel [2014]

Is that all there is?

The Bat Conservation Trust are calling for more records of bats roosting behind ivy. Crucially, records with a photo or video for verification – deadline 30 November 2025

Head over to the Bat Tree Habitat Key webpage to submit a records.  

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