Bats

Main Types of Bat Detectors

1. 

Heterodyne Detectors

• How they work: Tune manually to one frequency, shifting ultrasonic calls into audible range.
  
  
  

• Pros:
  
  
  

  • Simple, relatively inexpensive (~£80–£150).
    
    
    

  • Great for beginners and live listening.
    
    
    

• Cons:
  
  
  

  • Only hear one frequency at a time (easy to miss calls).
    
    
    

  • Hard to identify species accurately.
    
    
    

• Use case: Good for public engagement walks, but not for rigorous surveys.
  
  
  

2. 

Frequency Division (FD) Detectors

• How they work: Divide the ultrasonic call into a lower frequency, giving a real-time sound trace.
  
  
  

• Pros:
  
  
  

  • Continuous listening without needing to retune.
    
    
    

  • Usually cheaper than full-spectrum recorders.
    
    
    

• Cons:
  
  
  

  • Call quality is degraded, so species ID is less reliable.
    
    
    

• Use case: Training, citizen engagement, basic presence/absence.
  
  
  

3. 

Time Expansion (TE) Detectors

• How they work: Record a short ultrasonic clip, then slow it down for playback.
  
  
  

• Pros:
  
  
  

  • Very high quality recordings.
    
    
    

• Cons:
  
  
  

  • Expensive, and you can’t listen continuously.
    
    
    

• Use case: Specialist research, less common now (superseded by digital full-spectrum).
  
  
  

4. 

Full-Spectrum Recording Detectors

 (Static or handheld)

• How they work: Record the entire ultrasonic spectrum digitally for later analysis.
  
  
  

• Pros:
  
  
  

  • Best for species identification.
    
    
    

  • Data can be run through automated ID software (e.g. Kaleidoscope, SonoBat, BatClassify, or BTO’s Analook).
    
    
    

  • Models like Wildlife Acoustics Song Meter Mini Bat or Pettersson D500X can be left out for days/weeks.
    
    
    

• Cons:
  
  
  

  • More expensive (£300–£1000+).
    
    
    

  • Requires data processing.
    
    
    

• Use case: Ideal for long-term monitoring and scientific projects.
  
  
  

🏞 For Dùn Coillich (1,100 acres, community land, Highland Perthshire)

Since you’re looking at a large area, citizen science, and climate/biodiversity monitoring, the best balance is:

1. Static full-spectrum detectors – e.g. Wildlife Acoustics Song Meter Mini Bat (~£350–£400) or Audiomoth (~£80, but requires some DIY setup).
   
   
   

   • Can be deployed across different habitats (woodland edges, open hill, water bodies).
     
     
     

   • Capture data continuously overnight without supervision.
     
     
     

   • Good for building a long-term dataset.
     
     
     

2. Handheld heterodyne detectors – e.g. Batbox Duet or Magenta Bat5 (~£90–£120).
   
   
   

   • Perfect for guided bat walks with volunteers and community engagement.
     
     
     

👉 Combination approach works best:

• Static full-spectrum recorders for rigorous data.
  
  
  

• Handheld heterodyne detectors for public engagement.
  
  
  

⚖️ Cost/effort balance for a citizen science study

• If budget is limited: Audiomoth units are excellent (cheap, programmable, easy to deploy in multiple locations).
  
  
  

• If budget allows: Mix of 2–4 static Song Meter Minis plus a couple of handheld heterodyne detectors.
  
  
  

• Data analysis support: consider partnering with BCT (Bat Conservation Trust), Scottish Bat Workers’ Network, or BTO Scotland – they may help with training and/or analysis.
  
  
  

• ——————-

Goals (so the design fits the job)

1. Presence & relative activity of species across habitat types.
   
   
   

2. Year-to-year trend (phenology and activity changes).
   
   
   

3. Community engagement (guided walks + simple tasks for volunteers).
   
   
   

Likely species in Highland Perthshire (to guide tuning & analysis)

• Common pipistrelle (Pipistrellus pipistrellus) ~45 kHz peak
  
  
  

• Soprano pipistrelle (P. pygmaeus) ~55 kHz peak
  
  
  

• Daubenton’s bat (Myotis daubentonii) ~45–50 kHz, over water
  
  
  

• Brown long-eared (Plecotus auritus) quiet, broadband, lots of social calls
  
  
  

• Whiskered/Brandt’s (Myotis mystacinus/brandtii)—hard to separate acoustically
  
  
  

• Natterer’s possible in woodland; Noctule/Leisler’s occasional higher flyers
  
  
  

• Nathusius’ pipistrelle possible on autumn migration (Aug–Oct), esp. near water
  
  
  

Equipment mix that works

• Static full-spectrum recorders (core dataset):
  
  
  

  • 3–4× Wildlife Acoustics Song Meter Mini Bat or 6–10× AudioMoth (cheaper, more coverage).
    
    
    

  • 256–512 GB SD cards; weatherproofing (AudioMoth needs cases/desiccant).
    
    
    

• Handheld heterodyne detectors (for walks/training): 2× Magenta Bat5/BatBox Duet.
  
  
  

• Optional: 1 thermal monocular for engagement/safety near water.
  
  
  

Recorder settings (static): sample rate 384 kHz (or device max), triggered full-spectrum, medium gain; schedule: sunset–sunrise. Add a 5-min “calibration window” at dusk and at dawn (always-record) to standardise effort across nights.

Survey design (mix of static points + walked transects)

1) Stratify the site by habitat (map first)

Create 6 habitat strata (adjust to your map):

1. Woodland edge & rides
   
   
   

2. Riparian corridors (streams/burns)
   
   
   

3. Standing water (ponds/lochans, cattle troughs)
   
   
   

4. Open hill/rough grass/heath (edges, gullies)
   
   
   

5. Buildings & yard edges (if present)
   
   
   

6. Sheltered ecotones (woodland ↔ open mosaics)
   
   
   

2) Static deployment (rotating design for coverage)

• Grid the estate into 250 m cells (or use your existing management compartments).
  
  
  

• Pre-select 24 static points (4 per habitat type), with GPS and a brief site photo.
  
  
  

• Deploy 6 detectors per week (e.g., 6 AudioMoths or 3 Song Meter Minis moved twice as often), for 4 consecutive fair-weather nights each (= one “sample”).
  
  
  

• Rotate weekly so all 24 points get ≥4 nights within a 6–8-week window.
  
  
  

• Repeat this twice per season: May–June (breeding) and Aug–Sept (post-breeding/migration).
  
  
  

• Over a season you’ll accumulate ≈ 24 points × 8 nights = 192 detector-nights (good statistical power without being overwhelming).
  
  
  

Placement tips:

• Mount at 1.2–1.5 m on a stake/tree, mic angled slightly down, 2–3 m back from flyways; avoid foliage rub and water splash; keep away from continuous noise sources (fences, streams right beside the mic).
  
  
  

• For Daubenton’s, place 1–2 units on bridges/culverts or 1–2 m from the water edge facing along the channel.
  
  
  

• For open hill, target linear features (dry stone walls, gullies) and edge of bracken/heath rather than exposed tops.
  
  
  

• Record wind (Beaufort), rain, min temp nightly—activity is weather-sensitive.
  
  
  

3) Walked transects (volunteer-friendly, repeatable)

• Design two 2–3 km loops (60–90 min at a steady pace) covering:
  
  
  

  • Loop A: woodland edge → ride → water body.
    
    
    

  • Loop B: open mosaic → riparian corridor → edge.
    
    
    

• Start 30 min after sunset, walk at ~2–3 km/h.
  
  
  

• Each leader carries a heterodyne detector; tune around 45–55 kHz swapping as calls change (quick tip card below).
  
  
  

• Run each loop twice per month May–Sept.
  
  
  

• Log start/end time, temperature, wind, cloud, and noteworthy passes (you can also trail a lightweight recorder in a pocket for archiving).
  
  
  

Heterodyne quick-tune card (laminate):

• 55 kHz = Soprano pipistrelle (often by water/trees)
  
  
  

• 45 kHz = Common pipistrelle (ubiquitous edges)
  
  
  

• 35 kHz = Noctule/Leisler’s (fast, loud, above canopy)
  
  
  

• 45–50 kHz over smooth water = Daubenton’s (skimming)
  
  
  

• Lots of whispery rustles inside woods = Long-eared/Social calls → note location; rely on static recorders for ID later.
  
  
  

Season & timing

• Core window: May–September (Scotland).
  
  
  

• Avoid heavy rain and Beaufort >3.
  
  
  

• Prioritise warm, still nights after warm days.
  
  
  

• Consider an autumn Nathusius’ pipistrelle mini-project in Sept–Oct near water/valley corridors.
  
  
  

Data, metadata & QA (keep it simple but strict)

• File naming: DunCoillich_[HabitatCode]_[PointID]_[YYYYMMDD].wav
  
  
  

• Metadata sheet per unit: device ID, mic model, gain, height, orientation, GPS (WGS84), start/stop times, habitat, weather.
  
  
  

• Clock sync: sync all devices to BST/UTC before each deployment.
  
  
  

• Storage: central shared drive with a “raw / processed / reports” structure.
  
  
  

• Privacy/roosts: if roosts are discovered, mask precise coordinates in public outputs.
  
  
  

Analysis workflow (repeatable):

1. Automated pre-screen in Kaleidoscope/SonoBat/BatClassify to detect bat passes.
   
   
   

2. Species auto-ID with conservative thresholds.
   
   
   

3. Manual review of a subset (e.g., all Myotis and low-quality calls).
   
   
   

4. Metrics per night & point: passes/hour, species richness, first/last call time.
   
   
   

5. Visualise activity vs. habitat and weather; track year-on-year.
   
   
   

Volunteer structure

• Lead: 1 coordinator (schedules kit, collates data).
  
  
  

• Field team: 6–10 trained volunteers (buddy system at night).
  
  
  

• Analysts: 2–3 people trained on the software; set up a shared call library of verified exemplars from site.
  
  
  

• Engagement: monthly Bat Walk with heterodyne detectors + family-friendly ID sheets.
  
  
  

Minimal budgets (ballpark, ex-VAT)

• Cost-efficient (broad coverage):
  
  
  

  • 8× AudioMoth + cases/desiccant/SDs: ~£1,000
    
    
    

  • 2× heterodyne handsets: ~£220
    
    
    

  • Spares, batteries, posts, locks: ~£250
    
    
    

• Mid-range (fewer moves, less faff):
  
  
  

  • 3× Song Meter Mini Bat + SDs: ~£1,500–£1,800
    
    
    

  • 2× heterodyne handsets: ~£220
    
    
    

  • Spares & consumables: ~£300
    
    
    

• Optional: 1× thermal monocular (entry-level): ~£600–£1,200
  
  
  

Site-specific placement suggestions (Dùn Coillich)

If you have these features, try one point at each (rotate if units are limited):

1. Bridge/culvert on main burn (Daubenton’s).
   
   
   

2. Pond/lochans edge (pipistrelles + Myotis; Nathusius’ in autumn).
   
   
   

3. Sheltered woodland ride (long-eared, Natterer’s).
   
   
   

4. Woodland–open edge (pipistrelles activity hotspot).
   
   
   

5. Open gully/wall line on the hill (movement corridor).
   
   
   

6. Yard/buildings/old trees if present (prey & roosting opportunities).
   
   
   

Safety & permissions

• Lone-working policy; check-in/out.
  
  
  

• High-viz, headtorches, chest waders only if trained and never alone near water.
  
  
  

• Avoid nesting birds and scheduled features; follow landowner/committee protocols.
  
  
  

What you’ll get out of Year 1

• A site species list with confidence classes (certain/likely/indet.).
  
  
  

• Activity heatmap by habitat and season.
  
  
  

• A repeatable protocol for Year 2+ to detect change (climate/management effects).