How Many Bats Are in My Utah Attic? Colony Size Guide

One of the first questions Utah homeowners ask: “How bad is this?” Colony size varies from a handful to over a thousand animals. Here’s how to estimate what you’re dealing with.

Why Colony Size Matters

• Cost: 10 bats vs. 200 requires very different exclusion scope
• Cleanup: A 200-bat colony produces ~½ cubic foot of guano per month
• Health risk: Larger, older colonies carry greater histoplasmosis risk
• Complexity: Larger colonies typically use more entry points

Typical Utah Bat Colony Sizes by Species

Species	Typical Attic Colony	Max Observed
Big Brown Bat	20–100	300+
Little Brown Bat	100–500	1,500+
Yuma Myotis	50–300	600+
Brazilian Free-Tailed	100–1,000	Thousands

Signs That Indicate Larger Colony

• Guano more than ½ inch deep → multiple seasons, larger colony
• Multiple stained entry points → established, dispersed colony
• Significant chittering noise → suggests 50+ bats
• Colony present for 3+ years → 25% annual growth → originally 20 bats = 60+ now

How We Estimate Colony Size

Our free inspection includes: sunset exit count at all entry points, guano volume calculation, entry point usage intensity analysis, and attic temperature assessment. All included in your free written estimate.

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Utah Wildlife Specialists — Free colony size estimation with every inspection. UDWR Licensed. All of Utah.