Burrow-guarding constrains fights to duels and drives weapon evolution

Evidence

But tunnels also physically restrict access in a way that aligns the interactions of opponents. A rival male dung beetle has to enter the tunnel before he can challenge the guarding male. Ten males couldn’t attack at once even if they wanted to, because there isn’t space for more than one rival to enter at a time. The restricted confines of tunnels align battles so that they necessarily occur as a series of successive duels. Ball-rolling species, on the other hand, face no such restricted access. Males can challenge from all angles at once, and very often battles among ball rollers entail chaotic scrambles between three or four males. In dung beetles, species that fight one-on-one often have elaborate horns; species that fight in chaotic scrambles do not. — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 247 (#expands, via linked claim)

Burrows are probably the most widespread ecological situation leading to the evolution of extreme weapons. They are localized and readily defendable. Males can guard the entrances to tunnels where females reside, and in so doing, block rival males from approaching the females. … Although by no means a guarantee of weapon evolution, burrowing behavior provides two of the three critical prerequisites for an arms race, and this appears to have tipped the balance in species after species. — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 247 (#corroborates, via linked claim)

Categorization

• XREF: connects to: Burrowing is the most common ecology driving extreme weapon evolution. — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 247; Tunnel dwellers fight successive duels and evolve weapons; open-ground species scramble without them. — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 247; Concentrating simultaneous fire disfavors large weapons while duels favor them (+7 more)

Related

• Tunnel dwellers fight successive duels and evolve weapons; open-ground species scramble without them. (similarity 0.93)
• Burrowing is the most common ecology driving extreme weapon evolution. (similarity 0.92)
• Tunnel-bound fights give longer horns a decisive performance advantage (similarity 0.87)
• Tunneling dung beetles guard burrow entrances and evolve horns; rollers do not (similarity 0.86)
• Intense competition without duel structure does not drive weapon evolution. (similarity 0.82)
• Tunneling behavior predicts horn evolution in dung beetles (similarity 0.82)
• Animal and human fights both hinge on whether duels or gang-ups occur (similarity 0.81)
• One-on-one duels favor weapon evolution while chaotic scrambles do not. (similarity 0.80)
• Concentrating simultaneous fire disfavors large weapons while duels favor them (similarity 0.79)
• Dueling plus competition and defensibility is the general rule for extreme weapons (similarity 0.79)
• No ball-rolling dung beetle species has evolved horns despite constant fighting (similarity 0.78)

Broader Connections

• Tunnel dwellers fight successive duels and evolve weapons; open-ground species scramble without them. #expands (0.90) — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 247
• Concentrating simultaneous fire disfavors large weapons while duels favor them #corroborates (0.85)
• Burrowing is the most common ecology driving extreme weapon evolution. #corroborates (0.80) — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 247