At one time or another, solo women travelers will find themselves the object of curiosity – sometimes well intentioned, sometimes not. Avoidance is an easy, effective self-defense strategy. In the Andean region, particularly in smaller towns and rural areas, modest dress and conduct are the norm, while in Brazil and the more liberal Southern Cone, standards are more relaxed, especially in beach areas.
Machista (macho) attitudes, stressing masculine pride and virility, are fairly widespread among South American men (although less so in indigenous communities). They are often expressed by boasting and in exaggerated attention toward women. Snappy put-down lines or other caustic comebacks to unwanted advances may make the man feel threatened, and he may respond aggressively. Most women find it easier to invent a husband and leave the guy with his pride intact, especially in front of others.
There have been isolated cases of South American men raping women travelers. Women trekking or taking tours in remote or isolated areas should be especially cautious. Some cases have involved guides assaulting tour group members, so it's worth double-checking the identity and reputation of any guide or tour operator. Also be aware that women (and men) have been drugged, in bars and elsewhere, using drinks, cigarettes or pills. Police may not be very helpful in rape cases – if a local woman is raped, her family usually seeks revenge rather than calling the police. Tourist police may be more sympathetic, but it's possibly better to see a doctor and contact your embassy before reporting a rape to police.
Tampons are generally difficult to find in smaller towns, so stock up in cities or bring a supply from home. Birth control pills are sometimes tricky to find outside metropolitan areas, so you're best off bringing your own supply from home. If you can't bring enough, carry the original package with you so a pharmacist can match a local pill to yours.