N. lewisi Habitats and Behavior 



101 



There was some indication, however, that intruders may have used 

 olfaction in identifying an occupied territory. An intruder would touch 

 its snout to the gravel shelf or at the entrance. If the retreat was occu- 

 pied, the intruder usually moved hastily away from the area. 



An animal in residence when an intruder approached made a threat 

 display. Upon observing the intruder, the resident moved out of the 

 retreat opening so that its head and gills were exposed. The gills would 

 flare to the maximum level and slowly pulsate (Fig. 5). If the intruder 

 moved away or stopped, the resident would retreat into the opening. If 

 the intruder instead moved toward the entrance or approached the shelf 

 area, the threat was repeated. The resident would move out of the 

 retreat if an intruder was on the shelf or close to the opening. At this 

 time the resident's gills would be flared and rapidly pulsating, and occa- 

 sionally its upper lip would be curled (Fig. 6). This was done quite 

 rapidly, and usually indicated that an attack was imminent. This lip curl 

 display also was quite commonly seen when adult animals were handled, 

 but no animals ever attempted to bite during capture or handling. 



Attacks occurred in at least 50 percent of all intrusions observed. 

 Intrusions were quite rare, however, except when food or a new animal 

 was introduced into the tank. An attack would occur quite rapidly after 

 repeated threats and false charges. The resident animal would charge 



Fig. 5. Initial threat display to intruder by resident animal. 



