Technically speaking there is a difference between ethics, which is founded on language and argumentation, and altruism, which is behavior that is eusocial. In fact, altruism needn't even be psychological because it can occur at a biological level sufficiently far from consciousness (such as in ants) and is known as reciprocal altruism.
For something to be considered ethics it must according to IEP:
The field of ethics (or moral philosophy) involves systematizing, defending, and recommending concepts of right and wrong behavior.
Note that animals are not capable of arguing over concepts that require some form of grammar. Even other great apes who are capable of signing lack the capacity for ethical behavior based on their inability to use a full-fledged language that excludes signaling even with signs from sign language.
But animals are capable of eusocial behavior described well in E.O. Wilson's The Social Conquest of Earth, and ultimately that extends from at least ants to people.
In evolutionary biology, reciprocal altruism is a behaviour whereby an organism acts in a manner that temporarily reduces its fitness while increasing another organism's fitness, with the expectation that the other organism will act in a similar manner at a later time. The concept was initially developed by Robert Trivers to explain the evolution of cooperation as instances of mutually altruistic acts. The concept is close to the strategy of "tit for tat" used in game theory.
To understand the link between genes and behavior, one has to ultimately understand that genes express proteins in organisms that are correlated to behavior through heredity and learning. This is the subject of study in behavioral epigenetics.
Strictly speaking, ethicists divide ethics up into 3 major branches:
- Meta-ethics, concerning the theoretical meaning and reference of moral propositions, and how their truth values (if any) can be determined
- Normative ethics, concerning the practical means of determining a moral course of action
- Applied ethics, concerning what a person is obligated (or permitted) to do in a specific situation or a particular domain of action.
What all of these have in common is the use of reason, so without reason, there can be not ethics.