Organisms that obtain their food by feeding specifically on the faeces (excreta) of other animals are known by which term?

Introduction / Context:
Animals and microorganisms obtain food through a wide range of feeding strategies. Some species have evolved to feed on unusual materials that other organisms discard. One such strategy is consuming faeces or excreta of other animals. This question asks you to recall the specific term used in biology for organisms that feed on the excreta of other organisms as an important part of their diet.

Given Data / Assumptions:

The food source is faeces or excreta of other animals. We need a precise term, not just the general category of being a heterotroph. Options include autotrophs, heterotrophs, coprophagous organisms, saprotrophs and omnivores. We assume standard ecological terminology.

Concept / Approach:
Autotrophs are organisms that synthesise their own food from inorganic substances, usually using light or chemical energy. Heterotrophs obtain food from other organisms or organic material in general, which includes many feeding behaviours. Saprotrophs feed on dead and decaying organic matter, such as fallen leaves or carcasses, by external digestion. Omnivores eat both plant and animal matter. Organisms that specifically feed on faeces are called coprophagous (or coprophages). Dung beetles, some rodents and certain insects are classic examples of coprophagous organisms in ecology.

Step-by-Step Solution:
Step 1: Recognise that the question focuses on excreta or faeces as the primary food source. Step 2: Recall that the prefix copro refers to dung or faeces, and phagous refers to eating, giving coprophagous for dung eating organisms. Step 3: Note that autotrophs do not rely on excreta; they produce their own food. Step 4: Remember that while all coprophagous organisms are heterotrophs, the term heterotroph is too broad and not specific enough for this behaviour. Step 5: Recognise that saprotrophs and omnivores may consume various organic materials, but the technical term for faeces feeding is coprophagous.

Verification / Alternative check:
To verify, think about dung beetles rolling and burying animal droppings; these are always described in ecology texts as coprophagous insects. Similarly, some rodents such as rabbits practice coprophagy by re ingesting faecal pellets to extract more nutrients. In each of these examples, the term coprophagous is used rather than heterotroph or saprotroph, confirming that it is the correct and specific term for this feeding behaviour.

Why Other Options Are Wrong:
Autotrophs obtain energy from light or chemical reactions and build their own organic molecules, so they do not feed on excreta. Heterotrophs is a broad term for any organism that relies on external organic sources for food; it includes predators, herbivores, scavengers and coprophages, but does not specifically describe faeces feeding. Saprotrophs typically feed on dead and decaying matter, not on fresh faeces, which still contains undigested nutrients. Omnivores consume both plant and animal tissues but are not defined by eating excreta. These terms therefore do not accurately capture the specialised behaviour described in the question.

Common Pitfalls:
A common mistake is to choose heterotrophs or saprotrophs because they sound like general terms for non self feeding organisms. However, exam questions often look for the most specific term that fits the description. Another pitfall is not recognising the meaning of the prefix copro. Learning common biological prefixes and suffixes (such as auto, hetero, sapro and copro) can greatly help you decode unfamiliar terms and answer such questions correctly without rote memorisation.

Final Answer:
Organisms that feed on the excreta of other organisms are called coprophagous organisms.