Ingestion rate as Holling’s Type II functional response. More...

#include <foraging_limits.h>

Public Member Functions
	HalfMaxIntake (const double half_max_density, const double max_intake)
	Constructor. More...

double	get_intake_rate (const double density) const
	Get maximum daily net energy intake [unit as `max_intake`]. More...

Private Attributes
const double	half_max_density

const double	max_intake

Detailed Description

Ingestion rate as Holling’s Type II functional response.

The functional response of grazers (feeding rate depending on grass biomass) is usually described as a “Type II” of the types formulated by Crawford Stanley Holling (1959) [27].

Intake rate is expressed as a hyperbolically saturating (‘Michalig-Menten’) function:

$I = I_{max} * \frac{V}{V_{1/2} + V}$

$I_{max}$ is the maximum intake rate: the asymptote of the function curve. (gDM/m²) is the dry-matter forage (grass) density and $V_{1/2}$ (gDM/m²) is a species-specific half-saturation constant at which the herbivore reaches half of its maximum ingestion rate. This model is primarily empirical and does not represent any underlying mechanisms. The parameter $V_{1/2}$ does not generally scale with body mass and usually needs to be derived from field observations of the particular species.

Note: Illius & O’Connor (2000) and Pachzelt et al. (2013) also call $V_{1/2}$ “beta” (β).

See also: ForagingLimit::IlliusOConnor2000; ForagingLimit::GeneralFunctionalResponse

Constructor & Destructor Documentation

◆ HalfMaxIntake()

HalfMaxIntake::HalfMaxIntake	(	const double	half_max_density,
		const double	max_intake
	)

Constructor.

Parameters

half_max_density	The forage density at which the intake rate of a herbivore is half of its maximum. The unit can be freely chosen, but must correspond to the parameter `density` in get_intake_rate().
max_intake	Maximum intake rate; the asymptote of the functional response curve. The unit can be freely chosen as mass or energy per day or per minute etc.

Exceptions

std::invalid_argument If either half_max_density or max_intake is not a positive number.

Member Function Documentation

◆ get_intake_rate()

double HalfMaxIntake::get_intake_rate ( const double density ) const

Get maximum daily net energy intake [unit as max_intake].

Parameters

density Grass sward density [unit as half_max_density].

Returns: Realized feeding rate [unit as max_intake].

Exceptions

std::invalid_argument If density is negative.

Member Data Documentation

◆ half_max_density

const double Fauna::HalfMaxIntake::half_max_density

private

◆ max_intake

const double Fauna::HalfMaxIntake::max_intake